Amazon coding interview questions

902 DSA problems tagged as asked at Amazon, with statements, examples and constraints — practise free on CampusCode.

• 5. Remove Duplicates from Sorted Array Easy Array
• 6. Find the Missing Number Easy Array
• 8. Rotate Array by K Steps Easy Array
• 10. Merge Two Sorted Arrays Easy Array
• 12. Intersection of Two Arrays Easy Array
• 13. Find All Duplicates in Array Easy Array
• 15. Single Number (XOR Trick) Easy Array
• 16. Plus One Easy Array
• 17. Pascal's Triangle Row Easy Array
• 18. Contains Duplicate Easy Array
• 19. Best Time to Buy and Sell Stock Easy Array
• 20. Find the Pivot Index Easy Array
• 22. Shuffle the Array Easy Array
• 23. Running Sum of 1D Array Easy Array
• 24. Find Numbers with Even Number of Digits Easy Array
• 25. Squares of a Sorted Array Easy Array
• 26. Check if N and Its Double Exist Easy Array
• 27. Third Maximum Number Easy Array
• 28. Find All Numbers Disappeared in Array Easy Array
• 29. Height Checker Easy Array
• 30. Sum of All Odd Length Subarrays Easy Array
• 31. Kids With the Greatest Number of Candies Easy Array
• 33. Replace Elements with Greatest Element on Right Easy Array
• 34. Maximum Product of Two Elements in an Array Easy Array
• 35. Concatenation of Array Easy Array
• 36. Build Array from Permutation Easy Array
• 37. Richest Customer Wealth Easy Array
• 38. Find the Highest Altitude Easy Array
• 40. Find Center of Star Graph Easy Array
• 41. Flipping an Image Easy Array
• 42. Transpose Matrix Easy Array
• 44. Find Common Elements Between Two Arrays Easy Array
• 45. Count Good Pairs Easy Array
• 48. Find Smallest Letter Greater Than Target Easy Array
• 49. Matrix Diagonal Sum Easy Array
• 50. Sort Array by Parity Easy Array
• 51. Minimum Value to Get Positive Step by Step Sum Easy Array
• 52. Maximum Average Subarray I Easy Array
• 54. Max Consecutive Ones Easy Array
• 55. Left and Right Sum Differences Easy Array
• 56. Find Target Indices After Sorting Array Easy Array
• 57. Sum of Absolute Differences in Sorted Array Easy Array
• 58. Lucky Number in a Matrix Easy Array
• 59. Find the Array Concatenation Value Easy Array
• 60. Minimum Difference Between Highest and Lowest of K Scores Easy Array
• 61. Two Sum Easy Array
• 62. Three Sum Medium Array
• 63. Product of Array Except Self Medium Array
• 64. Subarray Sum Equals K Medium Array
• 65. Longest Subarray with Sum K Medium Array
• 66. Rotate Image (90 Degrees) Medium Array
• 67. Spiral Matrix Traversal Medium Array
• 68. Jump Game Medium Array
• 69. Container With Most Water Medium Array
• 70. Merge Intervals Medium Array
• 71. Insert Interval Medium Array
• 72. Sort Colors (Dutch National Flag) Medium Array
• 73. Find the Duplicate Number Medium Array
• 74. Maximum Subarray (Kadane's Algorithm) Medium Array
• 75. Longest Consecutive Sequence Medium Array
• 76. Set Matrix Zeroes Medium Array
• 77. Search in Rotated Sorted Array Medium Array
• 78. Find Peak Element Medium Array
• 79. Two Sum II - Input Array Is Sorted Medium Array
• 80. Minimum Size Subarray Sum Medium Array
• 81. Maximum Product Subarray Medium Array
• 82. Increasing Triplet Subsequence Medium Array
• 83. Next Permutation Medium Array
• 85. Minimum Number of Arrows to Burst Balloons Medium Array
• 86. Subsets Medium Array
• 87. Permutations Medium Array
• 88. Combination Sum Medium Array
• 89. Find First and Last Position of Element in Sorted Array Medium Array
• 90. Game of Life Medium Array
• 91. Summary Ranges Medium Array
• 92. 3Sum Closest Medium Array
• 93. 4Sum Medium Array
• 94. Maximum Points You Can Obtain from Cards Medium Array
• 95. Minimum Difference Between Largest and Smallest in Three Moves Medium Array
• 96. Max Number of K-Sum Pairs Medium Array
• 97. Count Number of Nice Subarrays Medium Array
• 98. Longest Mountain in Array Medium Array
• 99. Minimum Operations to Reduce X to Zero Medium Array
• 100. Maximum Width Ramp Medium Array
• 101. Find the Duplicate Number (Floyd's Cycle Detection) Medium Array
• 102. Array Nesting Medium Array
• 103. Shortest Unsorted Continuous Subarray Medium Array
• 104. Wiggle Sort II Medium Array
• 105. Trapping Rain Water Medium Array
• 106. Subarray Product Less Than K Medium Array
• 107. Minimum Path Sum Medium Array
• 108. Jump Game II Medium Array
• 109. Largest Rectangle in Histogram Medium Array
• 110. Median of Two Sorted Arrays Hard Array
• 111. First Missing Positive Hard Array
• 112. Best Time to Buy and Sell Stock III Hard Array
• 113. Sliding Window Maximum Hard Array
• 114. Candy Hard Array
• 115. Count of Smaller Numbers After Self Hard Array
• 116. Reverse Pairs Hard Array
• 117. Maximum Sum of 3 Non-Overlapping Subarrays Hard Array
• 118. Burst Balloons Hard Array
• 119. Best Time to Buy and Sell Stock IV Hard Array
• 120. Count of Range Sum Hard Array
• 121. Maximum Gap Hard Array
• 122. Shortest Subarray with Sum at Least K Hard Array
• 123. Count Inversions in Array Hard Array
• 124. Remove Boxes Hard Array
• 125. Candy Distribution Hard Array
• 126. Jump Game II (Minimum Jumps) Hard Array
• 127. Minimum Number of Refueling Stops Hard Array
• 128. Minimum Interval to Include Each Query Hard Array
• 130. Find K-th Smallest Pair Distance Hard Array
• 131. Find Minimum in Rotated Sorted Array II Hard Array
• 132. Patching Array Hard Array
• 133. Create Maximum Number Hard Array
• 134. Split Array Largest Sum Hard Array
• 135. Allocate Books (Binary Search + Greedy) Hard Array
• 136. Aggressive Cows Hard Array
• 137. Number of Subarrays with Bounded Maximum Hard Array
• 138. Minimum Cost to Hire K Workers Hard Array
• 139. Maximum Performance of a Team Hard Array
• 140. Minimize Max Distance to Gas Station Hard Array
• 141. Swim in Rising Water Hard Array
• 142. Minimum Moves to Equal Array Elements II Hard Array
• 143. Range Sum Query 2D Hard Array
• 144. Count Rectangles with All Ones Hard Array
• 145. Maximum Rectangle in Binary Matrix Hard Array
• 146. Shortest Common Supersequence via Array DP Hard Array
• 147. Strange Printer (Array Encoding) Hard Array
• 148. K-th Largest Element in a Stream (Array Variant) Hard Array
• 149. Minimum Window Subarray with All Distinct Elements Hard Array
• 150. Reverse a String Easy String
• 162. Roman to Integer Easy String
• 163. Longest Common Prefix Easy String
• 165. Valid Parentheses (String Version) Easy String
• 168. Count and Say Easy String
• 169. Merge Strings Alternately Easy String
• 171. Word Pattern Easy String
• 172. Find the Difference (One Extra Character) Easy String
• 173. Ransom Note Easy String
• 174. String Compression (Run-Length Encoding) Easy String
• 175. Repeated Substring Pattern Easy String
• 177. Maximum Nesting Depth of Parentheses Easy String
• 178. Find the Index of the First Occurrence in a String Easy String
• 180. Number of Segments in a String Easy String
• 185. Sorting the Sentence Easy String
• 187. Reverse Prefix of Word Easy String
• 188. Remove Vowels from String Easy String
• 189. Largest Odd Number in String Easy String
• 192. Check if Binary String Has at Most One Segment of Ones Easy String
• 195. String Without AAA or BBB Easy String
• 196. Concatenation of Consecutive Binary Numbers (String) Easy String
• 197. Check Distances Between Same Letters Easy String
• 199. Check if Two String Arrays are Equivalent Easy String
• 200. Make the String Great (Remove Same Adjacent) Easy String
• 202. Integer to Roman Easy String
• 203. Decode the Message Easy String
• 206. Minimum Number of Moves to Seat Everyone Easy String
• 207. Largest Number (Array to String Sort) Easy String
• 208. Decode String (Nested Brackets — Easy Variant) Easy String
• 209. Longest Substring with At Most Two Distinct Characters Easy String
• 211. Longest Palindromic Substring Medium String
• 212. Group Anagrams Medium String
• 213. Longest Palindrome by Rearranging Characters Medium String
• 214. Minimum Window Substring Medium String
• 215. String to Integer (atoi) Medium String
• 216. ZigZag Conversion Medium String
• 217. Multiply Strings Medium String
• 218. Decode Ways Medium String
• 219. Word Break Medium String
• 220. Generate Parentheses (Count) Medium String
• 221. Letter Combinations of a Phone Number (Count) Medium String
• 222. Restore IP Addresses (Count) Medium String
• 223. Count Palindromic Substrings Medium String
• 224. Longest Repeating Character Replacement Medium String
• 225. Valid Palindrome II Medium String
• 226. Palindrome Partitioning (Count) Medium String
• 227. Reorganize String (Feasibility) Medium String
• 228. Find All Anagrams in a String (Count) Medium String
• 229. Permutation in String Medium String
• 230. Compare Version Numbers Medium String
• 231. Reverse Words in a String Medium String
• 232. Simplify Path Medium String
• 233. Basic Calculator II Medium String
• 234. Decode String Medium String
• 235. Custom Sort String Medium String
• 236. Partition Labels (Count) Medium String
• 237. Count Distinct Subsequences (Modulo 10^9+7) Medium String
• 238. String Compression (Length) Medium String
• 239. Remove K Digits Medium String
• 240. Remove Duplicate Letters Medium String
• 241. Text Justification (Line Count) Medium String
• 242. Sort Characters By Frequency Medium String
• 243. Find the Index of the First Occurrence Medium String
• 244. Repeated DNA Sequences (Count) Medium String
• 245. Isomorphic Strings Medium String
• 246. Reverse Vowels of a String Medium String
• 247. Largest Number Medium String
• 248. Number of Distinct Substrings (Count) Medium String
• 249. Minimum Add to Make Parentheses Valid Medium String
• 250. Longest Substring with At Most K Distinct Characters Medium String
• 251. Substring with Concatenation of All Words (Count) Medium String
• 252. Find Longest Word by Deleting Characters Medium String
• 254. Maximum Number of Vowels in a Substring of Given Length Medium String
• 255. Defanging an IP Address Medium String
• 256. Bulls and Cows Medium String
• 257. Edit Distance Hard String
• 258. Wildcard Matching Hard String
• 259. Regular Expression Matching Hard String
• 260. Longest Valid Parentheses Hard String
• 261. Distinct Subsequences (Count Target in Source) Hard String
• 262. Word Break II (Count of Segmentations) Hard String
• 263. Shortest Palindrome (Prepend Count) Hard String
• 264. Palindrome Pairs (Count) Hard String
• 266. Scramble String Hard String
• 267. Interleaving String Hard String
• 268. Longest Duplicate Substring (Length) Hard String
• 269. Word Ladder (Shortest Transformation Length) Hard String
• 270. Concatenated Words (Count) Hard String
• 271. Valid Number Hard String
• 273. Palindrome Partitioning II (Minimum Cuts) Hard String
• 275. Last Substring in Lexicographical Order Hard String
• 276. Minimum Insertions to Make a Palindrome Hard String
• 277. Minimum Insertions to Balance Parentheses Hard String
• 278. Longest Substring with At Least K Repeating Characters Hard String
• 279. Basic Calculator Hard String
• 280. Different Ways to Add Parentheses (Count) Hard String
• 281. Expression Add Operators (Count) Hard String
• 283. Number of Ways to Form Target String (Modulo 10^9+7) Hard String
• 284. Stamping The Sequence (Stamp Count) Hard String
• 285. Integer to English Words Hard String
• 287. Number of Atoms Hard String
• 289. Distinct Subsequences II (Modulo 10^9+7) Hard String
• 290. Partition into Substrings with Unique Characters Hard String
• 291. Shortest Superstring (Length) Hard String
• 293. Longest Happy Prefix (Length) Hard String
• 294. Strong Password Checker (Minimum Steps) Hard String
• 295. Count Generalized Abbreviations (Modulo 10^9+7) Hard String
• 296. Special Binary String Hard String
• 315. Remove Nth Node from End of List Easy Linked List
• 316. Delete Middle Node of Linked List Easy Linked List
• 320. Swap Nodes in Pairs Easy Linked List
• 337. Remove Duplicates from Unsorted Linked List Easy Linked List
• 355. Merge K Sorted Linked Lists Medium Linked List
• 356. Reverse Linked List in Groups of K Medium Linked List
• 357. Add Two Numbers (Linked List Addition) Medium Linked List
• 358. Add Two Numbers II (No Reverse Allowed) Medium Linked List
• 359. Sort Linked List (Merge Sort) Medium Linked List
• 360. Reorder List Medium Linked List
• 361. Odd Even Linked List Medium Linked List
• 362. Rotate List by K Places Medium Linked List
• 363. Partition List Around a Value X Medium Linked List
• 364. Remove Linked List Elements by Value Medium Linked List
• 365. Linked List Cycle II (Start of Cycle) Medium Linked List
• 367. Delete Nodes Having Greater Value on Right Medium Linked List
• 368. Segregate 0s, 1s, and 2s in a Linked List Medium Linked List
• 369. Swap Nodes (Not Data) at Two Given Positions Medium Linked List
• 370. Reverse a Sub-list from Position M to N Medium Linked List
• 371. Pairwise Swap of Nodes Medium Linked List
• 372. Rearrange Linked List — Negatives Before Positives Medium Linked List
• 373. Delete N Nodes After M Nodes Medium Linked List
• 374. Check if Linked List is Sorted Medium Linked List
• 375. Skip M Delete N Nodes Medium Linked List
• 376. Find Length of Loop in Linked List Medium Linked List
• 377. Remove Zero-Sum Consecutive Nodes Medium Linked List
• 378. Sort a Linked List of 0s, 1s and 2s by Changing Links Medium Linked List
• 379. Next Greater Node in Linked List Medium Linked List
• 380. Maximum Twin Sum of a Linked List Medium Linked List
• 381. Split Linked List in Parts Medium Linked List
• 382. Rearrange Linked List to Alternating Low-High Medium Linked List
• 383. Count Nodes Deleted (Greater Value on Right) Medium Linked List
• 384. Convert Binary Number in Linked List to Integer Medium Linked List
• 385. Double a Number Represented as a Linked List Medium Linked List
• 386. Swapping Nodes in a Linked List (Values) Medium Linked List
• 387. Middle of the Linked List Medium Linked List
• 388. Palindrome Linked List (O(1) Space) Medium Linked List
• 389. Remove Nodes From Linked List (Monotonic Stack) Medium Linked List
• 390. Minimum Nodes to Remove for K Groups Medium Linked List
• 391. Merge Two Sorted Lists — Recursive Approach Medium Linked List
• 392. Reverse Alternate K Nodes Medium Linked List
• 394. Merge K Sorted Lists (Optimal — Min Heap) Hard Linked List
• 395. Reverse Nodes in K-Group (No Extra Space) Hard Linked List
• 396. Sort List in O(n log n) Time and O(1) Space Hard Linked List
• 397. Serialize and Deserialize Linked List Hard Linked List
• 398. Reverse Linked List in K-Groups (Reverse Remaining Too) Hard Linked List
• 399. Remove Duplicates from an Unsorted Linked List in O(n) Hard Linked List
• 400. Construct a Linked List from a 2D Matrix in Spiral Order Hard Linked List
• 401. Count Inversions via Merge Sort Hard Linked List
• 402. Largest Rectangle in Histogram (Stack) Hard Linked List
• 403. Josephus Problem Using Circular Linked List Hard Linked List
• 404. Merge M Sorted Lists of Variable Size Hard Linked List
• 405. Rearrange Linked List for In-Place Quicksort (Partition) Hard Linked List
• 406. Reverse a Linked List in Alternate Groups Hard Linked List
• 407. Sum of Two Numbers in Linked List Without Reverse Hard Linked List
• 408. Longest Palindrome in a Linked List Hard Linked List
• 409. Detect and Remove Loop — All Edge Cases Hard Linked List
• 410. Reorder List to Min-Max Interleaving Hard Linked List
• 411. Remove K Digits to Get Smallest Number (LL + Stack) Hard Linked List
• 412. Find All Anagrams via Sliding Window Hard Linked List
• 413. Find Kth Largest Using a Linked List Min-Heap Hard Linked List
• 414. Partition Linked List into K Consecutive Groups Hard Linked List
• 415. Reverse Every Alternate Group of K Nodes Hard Linked List
• 416. Maximum Sum Path in Two Sorted Linked Lists Hard Linked List
• 422. Find Smallest Letter Greater Than Target Easy Binary Search
• 427. Search Insert Position Easy Binary Search
• 428. Guess Number Higher or Lower Easy Binary Search
• 431. Count Negative Numbers in Sorted Matrix Easy Binary Search
• 436. Find Minimum in Rotated Sorted Array Easy Binary Search
• 437. Peak Index in a Mountain Array Easy Binary Search
• 438. Find in Mountain Array (Bitonic Search) Easy Binary Search
• 444. Arranging Coins (Binary Search Approach) Easy Binary Search
• 453. Two Sum in Sorted Array (Binary Search Variant) Easy Binary Search
• 454. Count Pairs Whose Sum is Less Than Target Easy Binary Search
• 456. Valid Perfect Square (BS Approach) Easy Binary Search
• 474. Search a 2D Matrix II (Row & Column Sorted) Easy Binary Search
• 475. Magnetic Force Between Two Balls (Introduction) Easy Binary Search
• 477. Find Peak Element in Array Medium Binary Search
• 478. Search in Rotated Sorted Array (With Duplicates) Medium Binary Search
• 479. Find Minimum in Rotated Sorted Array II (Duplicates) Medium Binary Search
• 480. Find K Closest Elements in Sorted Array Medium Binary Search
• 481. Capacity to Ship Packages Within D Days Medium Binary Search
• 482. Koko Eating Bananas Medium Binary Search
• 483. Minimum Number of Days to Make M Bouquets Medium Binary Search
• 484. Find the Smallest Divisor Given a Threshold Medium Binary Search
• 485. Aggressive Cows (Maximum Minimum Distance) Medium Binary Search
• 486. Allocate Books (Minimize Maximum Pages) Medium Binary Search
• 487. Split Array Largest Sum Medium Binary Search
• 488. Magnetic Force Between Two Balls Medium Binary Search
• 489. Gas Station — Minimum Stations to Add Medium Binary Search
• 490. Minimize Maximum Distance to Gas Station (Scaled) Medium Binary Search
• 491. Painter's Partition Problem Medium Binary Search
• 492. Matrix Median Medium Binary Search
• 493. Kth Element of Two Sorted Arrays Medium Binary Search
• 494. Find Nth Root of M (Binary Search on Answer) Medium Binary Search
• 495. EKO — Cutting Logs (Maximum Sawblade Height) Medium Binary Search
• 496. Minimum Time to Complete Trips Medium Binary Search
• 498. Maximum Candies Allocated to K Children Medium Binary Search
• 499. Maximize the Minimum After K Increments Medium Binary Search
• 500. Count of Pairs with Sum in a Range Medium Binary Search
• 501. Find the Duplicate Number (Binary Search on Value) Medium Binary Search
• 503. Find Right Interval Medium Binary Search
• 504. Random Pick with Weight (Deterministic Queries) Medium Binary Search
• 506. Longest Increasing Subsequence Length (Patience Sort + BS) Medium Binary Search
• 507. Russian Doll Envelopes (BS + Greedy) Medium Binary Search
• 508. Minimum Number of Operations to Make Array Continuous Medium Binary Search
• 511. Check If a Number Is a Majority Element in a Sorted Array Medium Binary Search
• 512. Heaters — Find the Minimum Radius Medium Binary Search
• 513. Maximum Side Length of a Square with Sum <= Threshold Medium Binary Search
• 516. Sqrt(x) with Precision (Binary Search on Float) Medium Binary Search
• 517. Count Pairs in Two Sorted Arrays Whose Sum is K Medium Binary Search
• 518. Weighted Job Scheduling (Binary Search + DP) Medium Binary Search
• 519. Minimum Operations to Reduce X to Zero Medium Binary Search
• 521. Maximum Number of Events That Can Be Attended Medium Binary Search
• 522. Minimum Eating Speed for All Piles Medium Binary Search
• 523. Course Schedule III (Greedy + Heap) Medium Binary Search
• 524. Search a 2D Matrix Medium Binary Search
• 525. Find First and Last Position of Element Medium Binary Search
• 526. Median of Two Sorted Arrays Hard Binary Search
• 527. Kth Smallest Element in a Sorted Matrix Hard Binary Search
• 528. Find K-th Smallest Pair Distance Hard Binary Search
• 529. K-th Smallest Number in Multiplication Table Hard Binary Search
• 530. Find in Mountain Array Hard Binary Search
• 531. Split Array Largest Sum (Optimal) Hard Binary Search
• 532. Count of Smaller Numbers After Self Hard Binary Search
• 533. Count of Range Sum Hard Binary Search
• 534. Reverse Pairs (Modified Merge Sort) Hard Binary Search
• 537. Minimum Interval to Include Each Query Hard Binary Search
• 538. Minimize Max Distance Between Gas Stations (Exact) Hard Binary Search
• 539. Minimum Window Containing All Required Elements Hard Binary Search
• 540. Find Kth Smallest Sum of a Matrix with Sorted Rows Hard Binary Search
• 541. Nth Magical Number Hard Binary Search
• 542. Swim in Rising Water Hard Binary Search
• 544. Max Sum of Rectangle No Larger Than K Hard Binary Search
• 545. Minimum Cost to Hire K Workers (Scaled) Hard Binary Search
• 546. Allocate Minimum Number of Pages (Multi-Constraint) Hard Binary Search
• 547. Koko Eating Bananas — Generalized K Piles Hard Binary Search
• 548. Minimum Total Distance Traveled Hard Binary Search
• 549. Special Array With X Elements Greater Than or Equal to X Hard Binary Search
• 550. Maximize the Minimum Powered City Hard Binary Search
• 551. Minimum Time to Repair Cars Hard Binary Search
• 553. Minimum Number of Refueling Stops Hard Binary Search
• 554. Minimum Limit of Balls in a Bag Hard Binary Search
• 555. Minimum Operations to Make Median of Array Equal to Target Hard Binary Search
• 556. Maximum Profit in Job Scheduling (Binary Search + DP) Hard Binary Search
• 557. Longest Substring with At Most K Replacements Hard Binary Search
• 558. Smallest Sufficient Team (Bitmask DP) Hard Binary Search
• 559. Guess the Word (Deterministic Strategy) Hard Binary Search
• 560. Minimize Deviation in Array Hard Binary Search
• 561. Minimum Number of Work Sessions to Finish the Tasks Hard Binary Search
• 563. K-th Lexicographically Smallest Integer in Range Hard Binary Search
• 575. Valid Parentheses (Multiple Types) Easy Stack
• 576. Remove All Adjacent Duplicates in String Easy Stack
• 577. Make String Great Easy Stack
• 584. Sliding Window Maximum Easy Stack
• 586. Time Needed to Buy Tickets Easy Stack
• 588. Number of Recent Calls Easy Stack
• 594. Next Greater Element I Easy Stack
• 598. Maximum Nesting Depth of Parentheses Easy Stack
• 604. Score of Parentheses Easy Stack
• 608. Next Greater Element II (Circular Array) Medium Stack
• 609. Daily Temperatures Medium Stack
• 610. Largest Rectangle in Histogram Medium Stack
• 611. Maximal Rectangle in Binary Matrix Medium Stack
• 612. Decode String (Nested Brackets) Medium Stack
• 613. Asteroid Collision Medium Stack
• 614. 132 Pattern Medium Stack
• 615. Remove Duplicate Letters Medium Stack
• 616. Online Stock Span Medium Stack
• 617. Max Width Ramp Medium Stack
• 618. Exclusive Time of Functions Medium Stack
• 619. Sum of Subarray Minimums Medium Stack
• 620. Sum of Subarray Maximums Medium Stack
• 621. Sliding Window Maximum (Monotonic Deque) Medium Stack
• 622. Task Scheduler (Greedy + Queue) Medium Stack
• 623. Jump Game VI (DP + Monotonic Deque) Medium Stack
• 624. Maximum of Minimum for Every Window Size Medium Stack
• 625. Dota2 Senate Medium Stack
• 626. Reveal Cards in Increasing Order Medium Stack
• 627. Design Snake Game Medium Stack
• 628. Open the Lock (BFS + Queue) Medium Stack
• 629. Car Fleet Medium Stack
• 630. Remove Nodes From Linked List Medium Stack
• 631. Number of Visible People in Queue Medium Stack
• 632. Build an Array With Stack Operations Medium Stack
• 633. Validate Stack Sequences Medium Stack
• 634. Count Collisions on a Road Medium Stack
• 635. Minimum Add to Make Parentheses Valid Medium Stack
• 636. Minimum Insertions to Balance Parentheses Medium Stack
• 637. Longest Valid Parentheses Medium Stack
• 638. Number of Atoms Medium Stack
• 639. Walls and Gates Medium Stack
• 640. Shortest Path in Binary Matrix Medium Stack
• 641. Perfect Squares Medium Stack
• 642. As Far from Land as Possible Medium Stack
• 643. Map of Highest Peak Medium Stack
• 646. Buildings With an Ocean View Medium Stack
• 647. Snakes and Ladders Medium Stack
• 648. Removing Stars From a String Medium Stack
• 649. Count of Students Unable to Eat Lunch Medium Stack
• 650. Minimum Number of Flips to Convert Binary Matrix to Zero Medium Stack
• 651. Check If Word Is Valid After Substitutions Medium Stack
• 652. Implement a Basic Calculator II Medium Stack
• 653. Trapping Rain Water Hard Stack
• 654. Largest Rectangle in Histogram (Optimal) Hard Stack
• 655. Maximal Rectangle Hard Stack
• 656. Basic Calculator I Hard Stack
• 657. Basic Calculator III Hard Stack
• 658. Longest Valid Parentheses (O(1) Space) Hard Stack
• 659. Remove Invalid Parentheses Hard Stack
• 660. Max Width Ramp (Optimal) Hard Stack
• 661. Count Submatrices With All Ones Hard Stack
• 662. Sum of Total Strength of Wizards Hard Stack
• 663. Number of Visible Pairs in a Queue Hard Stack
• 664. Maximum Score From Multiplication Operations Hard Stack
• 665. Minimum Swaps to Make String Balanced Hard Stack
• 666. Shortest Unsorted Continuous Subarray Hard Stack
• 668. Sliding Window Minimum and Maximum Together Hard Stack
• 669. Max Sum of Rectangle No Larger Than K Hard Stack
• 670. Minimum Cost Jump Game (Monotonic Queue DP) Hard Stack
• 671. Minimum Cost to Cut a Stick Hard Stack
• 672. Shortest Path in a Grid with Obstacles Elimination Hard Stack
• 673. Sliding Puzzle — Minimum Moves Hard Stack
• 674. Cut Off Trees for Golf Event Hard Stack
• 675. Minimum Genetic Mutation Hard Stack
• 676. Word Ladder — Shortest Transformation Hard Stack
• 677. Maximal Score After Applying K Operations Hard Stack
• 678. Count Subarrays With Score Less Than K Hard Stack
• 679. Maximum Robots Within Budget Hard Stack
• 680. Sum of Subarray Ranges Hard Stack
• 682. Maximum Points in an Archery Competition Hard Stack
• 683. Minimum Cost to Reach Destination in Time Hard Stack
• 685. Bus Routes Hard Stack
• 686. Flatten Binary Tree to Linked List Hard Stack
• 749. Generate All Subsets (Power Set) Medium Recursion
• 750. Generate All Unique Permutations of a String Medium Recursion
• 751. Generate All Unique Permutations of an Array Medium Recursion
• 752. Letter Combinations of a Phone Number Medium Recursion
• 753. Combination Sum I (Unlimited Use) Medium Recursion
• 754. Combination Sum II (Each Element Used Once) Medium Recursion
• 755. Combination Sum III (Exactly K Numbers) Medium Recursion
• 756. Subsets II (With Duplicates) Medium Recursion
• 757. Permutations II (With Duplicates) Medium Recursion
• 758. Palindrome Partitioning Medium Recursion
• 759. Word Search in 2D Grid Medium Recursion
• 760. N-Queens with Fixed First-Queen Column (Count Solutions) Medium Recursion
• 761. Rat in a Maze — Path Exists Medium Recursion
• 762. Sudoku Solver — Solvable? Medium Recursion
• 763. Count Balanced Parentheses (Catalan, Modulo 10^9+7) Medium Recursion
• 764. Decode Ways (Recursive + Memoization, Modulo 10^9+7) Medium Recursion
• 765. Word Break (Recursive + Memoization) Medium Recursion
• 766. Flood Fill Algorithm Medium Recursion
• 767. Merge Sort Medium Recursion
• 768. Quick Sort Medium Recursion
• 769. Climb Stairs with K Steps (Modulo 10^9+7) Medium Recursion
• 770. House Robber (Recursive + Memoization) Medium Recursion
• 771. Coin Change — Minimum Coins (Recursive) Medium Recursion
• 772. Coin Change II — Count Ways (Modulo 10^9+7) Medium Recursion
• 773. Unique Paths in Grid (Recursive, Modulo 10^9+7) Medium Recursion
• 774. Count Paths from Top-Left to Bottom-Right (Modulo 10^9+7) Medium Recursion
• 775. Knapsack 0/1 (Recursive + Memoization) Medium Recursion
• 776. Longest Common Subsequence (Recursive + Memoization) Medium Recursion
• 777. Longest Increasing Subsequence (Recursive + Memoization) Medium Recursion
• 778. Edit Distance (Recursive + Memoization) Medium Recursion
• 779. Count All Paths in Directed Graph (0 to N-1) Medium Recursion
• 780. Count Binary Strings Without Consecutive 1s (Modulo 10^9+7) Medium Recursion
• 781. Tower of Hanoi — General N Disks (Modulo 10^9+7) Medium Recursion
• 782. Count Distinct Subsequences of a String (Modulo 10^9+7) Medium Recursion
• 783. Count All Subsequences with Given Sum (Modulo 10^9+7) Medium Recursion
• 784. Check if Any Subsequence Equals Target Sum Medium Recursion
• 785. Kth Symbol in Grammar Medium Recursion
• 786. Gray Code — i-th Element Using Recursion Medium Recursion
• 787. Predict the Winner (Game Theory Recursion) Medium Recursion
• 788. Beautiful Arrangement — Count with First Value Fixed Medium Recursion
• 789. Wildcard Pattern Matching (? and *) Medium Recursion
• 790. Restore IP Addresses — Count Valid Decompositions Medium Recursion
• 791. Partition Equal Subset Sum (Recursive + Memo) Medium Recursion
• 792. Target Sum — Assign +/- to Each Number (Modulo 10^9+7) Medium Recursion
• 793. Count All Paths with Obstacles in Grid (Modulo 10^9+7) Medium Recursion
• 794. Count Islands Using DFS Recursion Medium Recursion
• 795. All Possible Full Binary Trees — Count Medium Recursion
• 796. Expression Add Operators — Count Expressions Reaching Target Medium Recursion
• 797. Minimum Path Sum in Grid (Recursive + Memoization) Medium Recursion
• 798. Josephus Problem Medium Recursion
• 799. N-Queens II — Count All Solutions (Optimized) Hard Recursion
• 800. Sudoku Solver (Optimized Backtracking) Hard Recursion
• 801. Regular Expression Matching (Recursive) Hard Recursion
• 802. Wildcard Matching (Recursive + Memo) Hard Recursion
• 803. Word Break II — Count All Sentences (Modulo 10^9+7) Hard Recursion
• 804. Remove Invalid Parentheses — Count Minimum-Removal Solutions Hard Recursion
• 805. K-th Permutation Sequence Hard Recursion
• 806. Burst Balloons (Interval DP via Recursion) Hard Recursion
• 807. Count All Valid Pickup/Delivery Options (Modulo 10^9+7) Hard Recursion
• 808. Knight Dialer — Count Distinct Sequences (Modulo 10^9+7) Hard Recursion
• 810. Reconstruct Itinerary — Euler Path Exists from JFK Hard Recursion
• 811. Shortest Path Visiting All Nodes (Recursion + Bitmask) Hard Recursion
• 813. Count Arrangements of N Bishops on M×M Board Hard Recursion
• 814. Beautiful Arrangement II — Constructible? Hard Recursion
• 815. Minimum Cost to Fill Given Weight in Bag Hard Recursion
• 816. Partition to K Equal Sum Subsets Hard Recursion
• 817. Matchsticks to Square (Backtracking) Hard Recursion
• 819. Tiling Problem — Count Ways to Tile 2×N Floor (Modulo 10^9+7) Hard Recursion
• 820. Egg Drop Problem (Recursive + Memo) Hard Recursion
• 821. Optimal Strategy for a Game (Coin Row) Hard Recursion
• 822. Super Egg Drop (Binary Search + Recursion) Hard Recursion
• 823. Maximum Sum Increasing Subsequence (Recursive) Hard Recursion
• 824. Count Strings Without 3 Consecutive Same Characters (Modulo 10^9+7) Hard Recursion
• 825. Find All Paths in DAG (Count, u to v) Hard Recursion
• 826. Minimum XOR Sum of Two Arrays (Bitmask Recursion) Hard Recursion
• 827. Allocate Mailboxes — DP on Sorted Array Hard Recursion
• 828. All Paths for a Sum in Binary Tree Hard Recursion
• 829. Minimum Moves to Spread Stones Over 3×3 Grid Hard Recursion
• 831. Print All K-Partitions of a String — Count (Mod 10^9+7) Hard Recursion
• 832. Zuma Game (Recursive DP) Hard Recursion
• 833. Strange Printer (Recursive Interval DP) Hard Recursion
• 834. Maximum Product of Splitted Binary Tree (Mod 10^9+7) Hard Recursion
• 840. Minimum Depth of Binary Tree Easy Trees
• 848. Diameter of Binary Tree Easy Trees
• 875. Search in Binary Search Tree Easy Trees
• 876. Insert into Binary Search Tree Easy Trees
• 881. Inorder Successor in BST Easy Trees
• 885. Kth Smallest Element in BST Easy Trees
• 895. Binary Tree Maximum Path Sum Medium Trees
• 896. Construct Binary Tree from Preorder and Inorder Medium Trees
• 897. Construct Binary Tree from Postorder and Inorder Medium Trees
• 898. Flatten Binary Tree to Linked List Medium Trees
• 899. Populating Next Right Pointers in Each Node Medium Trees
• 900. Binary Tree Right Side View Medium Trees
• 901. Sum Root to Leaf Numbers Medium Trees
• 902. Path Sum II — All Root-to-Leaf Paths Medium Trees
• 903. Path Sum III — Any Downward Path Medium Trees
• 904. Count Good Nodes in Binary Tree Medium Trees
• 905. All Nodes Distance K in Binary Tree Medium Trees
• 906. Find Duplicate Subtrees Medium Trees
• 907. Maximum Difference Between Node and Ancestor Medium Trees
• 908. Time to Burn Binary Tree from a Node Medium Trees
• 909. Morris Inorder Traversal (O(1) Space) Medium Trees
• 910. Morris Preorder Traversal (O(1) Space) Medium Trees
• 911. Iterative Postorder Using One Stack Medium Trees
• 912. Vertical Order Traversal (Coordinate Sort) Medium Trees
• 913. Check if Two Trees are Isomorphic Medium Trees
• 914. Minimum Time to Collect All Apples Medium Trees
• 915. Longest Univalue Path Medium Trees
• 916. House Robber III — Tree DP Medium Trees
• 917. Distribute Coins in Binary Tree Medium Trees
• 918. Delete Node and Return Forest Medium Trees
• 919. Recover BST — Two Swapped Nodes Medium Trees
• 920. Convert Sorted List to BST Medium Trees
• 921. Convert BST to Greater Tree Medium Trees
• 922. Balance a Binary Search Tree Medium Trees
• 923. Merge Two BSTs Medium Trees
• 926. Closest BST Values II — K Closest Medium Trees
• 927. BST Iterator (In-Order Lazy Evaluation) Medium Trees
• 928. Count Words with Given Prefix in Trie Medium Trees
• 929. Longest Word in Dictionary (Trie) Medium Trees
• 930. Replace Words Using Trie (Sentence Shortening) Medium Trees
• 931. Range Sum Query — Segment Tree Build Medium Trees
• 932. Binary Indexed Tree — Prefix Sum Medium Trees
• 933. Pseudo-Palindromic Paths in Binary Tree Medium Trees
• 934. Even Odd Tree Medium Trees
• 935. Check Completeness of a Binary Tree Medium Trees
• 936. Binary Tree Maximum Path Sum (Any to Any) Hard Trees
• 937. Recover BST — O(1) Space Morris Hard Trees
• 938. Count of Smaller Numbers After Self (BST/BIT) Hard Trees
• 939. Vertical Order Traversal (Full Coordinate Sort) Hard Trees
• 940. Time to Burn Tree — Multi-Source BFS Hard Trees
• 941. All Possible Full Binary Trees (Count) Hard Trees
• 942. Maximum Sum BST in Binary Tree Hard Trees
• 943. Linked List in Binary Tree Hard Trees
• 944. Number of Ways to Reorder Array as BST Hard Trees
• 945. Count of Range Sum (Merge Sort + BST) Hard Trees
• 946. Kth Smallest in Lexicographic Order Hard Trees
• 947. Convert BST to Sorted Doubly Linked List Hard Trees
• 948. Palindrome Pairs (Trie Approach) Hard Trees
• 949. Stream of Characters (Aho-Corasick Lite) Hard Trees
• 950. Maximum XOR of Two Numbers (Trie Bitwise) Hard Trees
• 952. Range Minimum Query (Segment Tree) Hard Trees
• 953. Count of Range Sum (Segment Tree) Hard Trees
• 954. Number of Longest Increasing Subsequences Hard Trees
• 955. Rectangle Area II — Coordinate Compression Hard Trees
• 956. Count Inversions Using BIT Hard Trees
• 957. Kth Smallest Element in a Sorted Matrix Hard Trees
• 958. 2D Range Sum Queries (2D BIT / Prefix) Hard Trees
• 959. Lowest Common Ancestor Using Binary Lifting Hard Trees
• 960. LCA + Distance Queries on a Tree Hard Trees
• 961. Maximum Weight Independent Set on a Tree Hard Trees
• 962. Tree Diameter with Weighted Edges Hard Trees
• 963. Minimum Vertex Cover on a Tree Hard Trees
• 964. Minimum Dominating Set on a Tree Hard Trees
• 965. Sum of Distances in Tree (Rerooting) Hard Trees
• 966. Find Duplicate Subtrees (Hashing) Hard Trees
• 967. Distribute Coins in Binary Tree (Minimum Moves) Hard Trees
• 989. Number of Islands (DFS) Easy Graphs
• 991. Max Area of Island Easy Graphs
• 994. Pacific Atlantic Water Flow Easy Graphs
• 997. Shortest Path in Binary Matrix Easy Graphs
• 999. Island Perimeter Easy Graphs
• 1000. Number of Closed Islands Easy Graphs
• 1001. Number of Enclaves Easy Graphs
• 1002. Count Sub Islands Easy Graphs
• 1003. Map of Highest Peak (BFS) Easy Graphs
• 1023. Redundant Connection Easy Graphs
• 1026. Dijkstra's Shortest Path Algorithm Medium Graphs
• 1027. Bellman-Ford Shortest Path Medium Graphs
• 1028. Shortest Path in DAG (Topo + Relax) Medium Graphs
• 1029. Floyd-Warshall All-Pairs Shortest Path Medium Graphs
• 1030. Dijkstra on Grid — Minimum Cost Path Medium Graphs
• 1031. Network Delay Time (Dijkstra) Medium Graphs
• 1032. Cheapest Flights Within K Stops Medium Graphs
• 1033. Path with Minimum Effort Medium Graphs
• 1034. Swim in Rising Water (Dijkstra / BS) Medium Graphs
• 1035. Find the City with Smallest Reachable Neighbours Medium Graphs
• 1036. Minimum Spanning Tree — Kruskal's Algorithm Medium Graphs
• 1037. Minimum Spanning Tree — Prim's Algorithm Medium Graphs
• 1038. Minimum Cost to Connect All Points Medium Graphs
• 1039. Critical Connections — Bridges in Graph Medium Graphs
• 1040. Minimum Spanning Tree — Number of Edges Medium Graphs
• 1041. Course Schedule II — Return Order Medium Graphs
• 1042. Alien Dictionary — Find Letter Order Medium Graphs
• 1043. Find All Ancestors of a Node in DAG Medium Graphs
• 1044. Parallel Courses — Minimum Semesters Medium Graphs
• 1045. Sequence Reconstruction Using Topo Sort Medium Graphs
• 1046. Kosaraju's Algorithm — Strongly Connected Components Medium Graphs
• 1047. Tarjan's Algorithm — SCC Medium Graphs
• 1048. Count Strongly Connected Components Medium Graphs
• 1049. Accounts Merge Medium Graphs
• 1050. Satisfiability of Equality Equations Medium Graphs
• 1051. Number of Islands II (Dynamic) Medium Graphs
• 1053. Making a Large Island Medium Graphs
• 1054. Word Ladder II — All Shortest Paths Medium Graphs
• 1055. Open the Lock — Minimum Turns Medium Graphs
• 1056. Minimum Jumps to Reach End (Jump Game BFS) Medium Graphs
• 1057. Snakes and Ladders Medium Graphs
• 1058. Bus Routes — Minimum Buses to Destination Medium Graphs
• 1059. Shortest Path Visiting All Nodes (Bitmask BFS) Medium Graphs
• 1060. Number of Provinces — Connected Components Medium Graphs
• 1061. Keys and Rooms Medium Graphs
• 1062. Find Eventual Safe States Medium Graphs
• 1063. Reconstruct Itinerary (Eulerian Path) Medium Graphs
• 1064. Graph Valid Tree Medium Graphs
• 1066. As Far from Land as Possible Medium Graphs
• 1067. Minimum Obstacles to Reach Corner (0-1 BFS) Medium Graphs
• 1068. Cut Off Trees for Golf Event Medium Graphs
• 1069. Minimum Cost to Make at Least One Valid Path Medium Graphs
• 1071. Graph Coloring — M-Coloring Problem Medium Graphs
• 1072. Check if Graph is Bipartite (BFS) Medium Graphs
• 1073. Number of Ways to Arrive at Destination Medium Graphs
• 1074. Minimum Weighted Sum to All Reachable Nodes Medium Graphs
• 1075. Check Connectivity After Node Removal Medium Graphs
• 1076. Dijkstra with State — Minimum Cost with K Stops Hard Graphs
• 1077. Bellman-Ford — Detect Negative Weight Cycle Hard Graphs
• 1078. Johnson's Algorithm — All-Pairs on Sparse Graph Hard Graphs
• 1079. Minimum Cost Path with At Most K Edges (DP+Graph) Hard Graphs
• 1080. Max Flow — Ford-Fulkerson Algorithm Hard Graphs
• 1081. Max Flow — Edmonds-Karp (BFS-based) Hard Graphs
• 1082. Minimum Cut in a Flow Network Hard Graphs
• 1083. Bipartite Matching — Maximum Matching Hard Graphs
• 1084. Minimum Path Cover in DAG Hard Graphs
• 1085. Minimum Edges to Make Graph Strongly Connected Hard Graphs
• 1086. Count Critical Nodes Whose Removal Disconnects Graph Hard Graphs
• 1087. 2-SAT Problem Using Implication Graph Hard Graphs
• 1088. Minimum Height Trees — Topological Trim Hard Graphs
• 1089. Parallel Courses III — Maximum Time with Dependencies Hard Graphs
• 1090. Second Best Minimum Spanning Tree Hard Graphs
• 1091. Maximum Spanning Tree Hard Graphs
• 1092. Connecting Cities With Minimum Cost Hard Graphs
• 1093. DSU with Rollback — Online Connectivity Hard Graphs
• 1094. Connected Components After Edge Removals (Offline) Hard Graphs
• 1095. Genetic Mutation — Minimum Mutations (BFS) Hard Graphs
• 1096. Shortest Bridge Hard Graphs
• 1097. Number of Restricted Paths Hard Graphs
• 1098. Jump Game IV — BFS with Value Groups Hard Graphs
• 1099. Shortest Path with Obstacle Elimination Hard Graphs
• 1100. Cherry Pickup II — Two Robots Hard Graphs
• 1101. Minimum Days to Disconnect Island Hard Graphs
• 1103. Course Schedule IV — Reachability Queries Hard Graphs
• 1104. Find All Bridges Using Tarjan's Algorithm Hard Graphs
• 1105. Articulation Points Using Tarjan's Algorithm Hard Graphs
• 1106. Eulerian Circuit Using Hierholzer's Algorithm Hard Graphs
• 1107. Hamiltonian Path Existence (Bitmask DP) Hard Graphs
• 1108. Travelling Salesman Problem (Bitmask DP) Hard Graphs
• 1109. Count Hamiltonian Paths in DAG (Bitmask DP) Hard Graphs
• 1111. General Graph Maximum Matching Hard Graphs
• 1112. Max Stones Removed with Same Row or Column Hard Graphs
• 1113. Couples Holding Hands — Minimum Swaps Hard Graphs
• 1114. Minimum Equivalent Graph via Transitive Reduction Hard Graphs
• 1115. Climbing Stairs Easy Dynamic Programming
• 1117. Fibonacci Number (Bottom-Up DP) Easy Dynamic Programming
• 1119. Min Cost Climbing Stairs Easy Dynamic Programming
• 1121. House Robber II (Circular Array) Easy Dynamic Programming
• 1129. Get Maximum in Generated Array Easy Dynamic Programming
• 1131. Divisor Game Easy Dynamic Programming
• 1143. Minimum Falling Path Sum Easy Dynamic Programming
• 1166. Longest Palindromic Subsequence Easy Dynamic Programming
• 1170. Wildcard Matching (? and *) Easy Dynamic Programming
• 1171. Regular Expression Matching (. and *) Easy Dynamic Programming
• 1172. Edit Distance (Levenshtein) Easy Dynamic Programming
• 1173. Interleaving String Easy Dynamic Programming
• 1174. Scramble String Easy Dynamic Programming
• 1175. Best Time to Buy and Sell Stock I Medium Dynamic Programming
• 1176. Best Time to Buy and Sell Stock II — Unlimited Medium Dynamic Programming
• 1177. Best Time to Buy and Sell Stock III — At Most 2 Medium Dynamic Programming
• 1178. Best Time to Buy and Sell Stock IV — At Most K Medium Dynamic Programming
• 1179. Buy and Sell with Cooldown Medium Dynamic Programming
• 1180. Buy and Sell with Transaction Fee Medium Dynamic Programming
• 1181. Longest Increasing Subsequence — O(n log n) Medium Dynamic Programming
• 1182. Longest Decreasing Subsequence Medium Dynamic Programming
• 1183. Longest Bitonic Subsequence Medium Dynamic Programming
• 1184. Number of Longest Increasing Subsequences Medium Dynamic Programming
• 1185. Largest Divisible Subset Medium Dynamic Programming
• 1186. Russian Doll Envelopes Medium Dynamic Programming
• 1187. Maximum Length of Pair Chain Medium Dynamic Programming
• 1188. Minimum Number of Removals to Make Mountain Array Medium Dynamic Programming
• 1189. Matrix Chain Multiplication Medium Dynamic Programming
• 1190. Burst Balloons Medium Dynamic Programming
• 1191. Minimum Cost to Merge Stones Medium Dynamic Programming
• 1192. Palindrome Partitioning II — Min Cuts Medium Dynamic Programming
• 1193. Strange Printer Medium Dynamic Programming
• 1194. Zuma Game Medium Dynamic Programming
• 1195. Minimum Score Triangulation of Polygon Medium Dynamic Programming
• 1197. Predict the Winner Medium Dynamic Programming
• 1198. Stone Game I Medium Dynamic Programming
• 1199. House Robber III — Tree DP Medium Dynamic Programming
• 1200. Diameter of Binary Tree (DP) Medium Dynamic Programming
• 1201. Maximum Independent Set on Tree Medium Dynamic Programming
• 1202. Distribute Coins in Binary Tree Medium Dynamic Programming
• 1203. Minimum Time to Collect All Apples Medium Dynamic Programming
• 1204. Count Paths in DAG with Constraints Medium Dynamic Programming
• 1205. Longest Path in a DAG Medium Dynamic Programming
• 1206. Minimum Jumps to Reach End (Graph DP) Medium Dynamic Programming
• 1207. Weighted Job Scheduling (DP + Binary Search) Medium Dynamic Programming
• 1208. Maximum Profit in Job Scheduling Medium Dynamic Programming
• 1209. Partition to K Equal Sum Subsets Medium Dynamic Programming
• 1210. Partition Array for Maximum Sum Medium Dynamic Programming
• 1211. Maximum Subarray Sum (Kadane's — DP View) Medium Dynamic Programming
• 1212. Maximum Sum Circular Subarray Medium Dynamic Programming
• 1213. Maximum Product Subarray Medium Dynamic Programming
• 1214. Maximum Score After Splitting String Medium Dynamic Programming
• 1215. Split Array Largest Sum (Binary Search + DP) Medium Dynamic Programming
• 1216. Minimum Cost to Cut a Stick Medium Dynamic Programming
• 1217. Dungeon Game — Minimum Health Medium Dynamic Programming
• 1218. Cherry Pickup I — Two-Pass DP Medium Dynamic Programming
• 1219. Maximum Points You Can Obtain from Cards Medium Dynamic Programming
• 1220. Count Vowels Permutations Medium Dynamic Programming
• 1221. Count Square Submatrices with All Ones Medium Dynamic Programming
• 1222. Maximal Square of Ones in Matrix Medium Dynamic Programming
• 1224. Number of Submatrices That Sum to Target Medium Dynamic Programming
• 1225. Travelling Salesman Problem (TSP) Hard Dynamic Programming
• 1226. Minimum Cost to Visit Every Node Hard Dynamic Programming
• 1227. Shortest Path Visiting All Nodes (BFS + Bitmask) Hard Dynamic Programming
• 1228. Partition Into Two Arrays to Minimize Sum Difference Hard Dynamic Programming
• 1229. Count Ways to Assign Tasks to Workers Hard Dynamic Programming
• 1231. Beautiful Arrangement — Count Permutations Hard Dynamic Programming
• 1232. Number of Ways to Paint N x 3 Grid Hard Dynamic Programming
• 1233. Count Numbers with Unique Digits Hard Dynamic Programming
• 1234. Count Digit One — Numbers from 1 to N Hard Dynamic Programming
• 1235. Numbers at Most N Given Digit Set Hard Dynamic Programming
• 1236. Non-Negative Integers without Consecutive Ones Hard Dynamic Programming
• 1238. K-th Smallest in Lexicographic Order Hard Dynamic Programming
• 1239. Word Break II — All Sentence Splits Hard Dynamic Programming
• 1240. Palindrome Pairs Hard Dynamic Programming
• 1241. Distinct Subsequences II Hard Dynamic Programming
• 1244. Shortest Common Supersequence — Print Hard Dynamic Programming
• 1245. Longest Common Subsequence of Three Strings Hard Dynamic Programming
• 1246. String Compression II Hard Dynamic Programming
• 1247. Stone Game II Hard Dynamic Programming
• 1248. Stone Game III Hard Dynamic Programming
• 1251. Nim Game Generalization Hard Dynamic Programming
• 1252. Grundy Number and Sprague-Grundy Theorem Hard Dynamic Programming
• 1253. Cherry Pickup II — Two Robots Hard Dynamic Programming
• 1254. Minimum Difficulty of a Job Schedule Hard Dynamic Programming
• 1255. Allocate Mailboxes Hard Dynamic Programming
• 1256. Minimum Total Distance Traveled Hard Dynamic Programming
• 1257. Paint House III — K Colours Hard Dynamic Programming
• 1259. 3D Knapsack — Two Constraints Hard Dynamic Programming
• 1260. Minimum Number of Work Sessions Hard Dynamic Programming
• 1261. Tallest Billboard Hard Dynamic Programming
• 1262. Last Stone Weight II Hard Dynamic Programming
• 1263. Ones and Zeroes Hard Dynamic Programming
• 1264. Super Egg Drop Hard Dynamic Programming
• 1306. Missing Number in Array (XOR Approach) Easy Bit Manipulation
• 1319. Binary Number with Alternating Bits Easy Bit Manipulation
• 1325. Subsets Generation Using Bitmask Medium Bit Manipulation
• 1326. Check if a Set is a Subset of Another Medium Bit Manipulation
• 1327. Count Subsets with Given XOR Medium Bit Manipulation
• 1328. Count Subsets with Given AND Value Medium Bit Manipulation
• 1329. Power Set Using Bitmask Medium Bit Manipulation
• 1330. Beautiful Arrangement — Bitmask Backtracking Medium Bit Manipulation
• 1331. Partition Array into Two Subsets with Min Diff Medium Bit Manipulation
• 1332. Count of Pairs with AND Equal to Zero Medium Bit Manipulation
• 1333. Maximum AND Value of a Pair in Array Medium Bit Manipulation
• 1334. Maximum XOR of Two Numbers in Array (Trie) Medium Bit Manipulation
• 1335. Maximum XOR of Element with Array (Query) Medium Bit Manipulation
• 1336. Single Number II — Element Appears Three Times Medium Bit Manipulation
• 1337. Single Number III — Two Elements Appear Once Medium Bit Manipulation
• 1338. Decode XOR Encoded Array Medium Bit Manipulation
• 1339. Find XOR of All Permutations Medium Bit Manipulation
• 1340. XOR Queries of a Subarray Medium Bit Manipulation
• 1341. Minimum Number of Flips to Make OR of Array K Medium Bit Manipulation
• 1343. Count Numbers with Unique Digits (Bitmask DP) Medium Bit Manipulation
• 1344. Partition Into Two Arrays to Minimize Sum Diff Medium Bit Manipulation
• 1345. Stickers to Spell Word — Bitmask DP Medium Bit Manipulation
• 1347. Count Strings Without Consecutive 1s Medium Bit Manipulation
• 1349. Minimum Cost to Visit Every Node (Bitmask TSP) Medium Bit Manipulation
• 1350. Find Minimum Time to Finish All Jobs Medium Bit Manipulation
• 1352. Add Two Numbers Without Arithmetic Operators Medium Bit Manipulation
• 1353. Subtract Using Bitwise Operators Only Medium Bit Manipulation
• 1354. Multiply Two Numbers Using Bit Shifts Medium Bit Manipulation
• 1355. Divide Two Integers Without / Operator Medium Bit Manipulation
• 1356. Compute Power x^n Using Bits (Fast Exponent) Medium Bit Manipulation
• 1357. Multiply 64-bit Integers Without Overflow Medium Bit Manipulation
• 1358. Generate Gray Code Sequence Medium Bit Manipulation
• 1359. Find Nth Gray Code Number Medium Bit Manipulation
• 1360. Circular Permutation in Binary Representation Medium Bit Manipulation
• 1361. Bitwise AND of Numbers Range Medium Bit Manipulation
• 1362. Count Bit Changes to Sort Array Medium Bit Manipulation
• 1363. Minimum Number of Operations to Make XOR Zero Medium Bit Manipulation
• 1364. Largest Combination with Bitwise AND Greater Zero Medium Bit Manipulation
• 1365. Count Integers in Range with Popcount Condition Medium Bit Manipulation
• 1366. Find Two Numbers with Odd Occurrences Medium Bit Manipulation
• 1367. Bit Reversal of 32-bit Integer Medium Bit Manipulation
• 1368. UTF-8 Validation Using Bit Masking Medium Bit Manipulation
• 1369. Integer Replacement — Min Steps Using Bits Medium Bit Manipulation
• 1370. Decode XOR Encoded Permutation Medium Bit Manipulation
• 1372. Travelling Salesman — Classic Bitmask DP Hard Bit Manipulation
• 1373. Assignment Problem — Min Cost Bitmask DP Hard Bit Manipulation
• 1374. Cover All Nodes with Minimum Edges (Bitmask) Hard Bit Manipulation
• 1375. Minimum XOR Sum of Two Arrays Hard Bit Manipulation
• 1376. Minimum Number of Work Sessions (Bitmask) Hard Bit Manipulation
• 1378. Can I Win (Bitmask Game DP) Hard Bit Manipulation
• 1379. Zuma Game — Bitmask Interval DP Hard Bit Manipulation
• 1380. Matching with Weighted Bipartite Graph Hard Bit Manipulation
• 1381. Count All Valid Pickup Delivery Orders Hard Bit Manipulation
• 1382. Find Minimum Number of Coins for Each Amount Hard Bit Manipulation
• 1383. Shortest Path Visiting All Nodes Hard Bit Manipulation
• 1384. Count Ways to Assign Tasks — K Workers Hard Bit Manipulation
• 1385. Parallel Courses III — Bitmask Scheduling Hard Bit Manipulation
• 1386. Maximum XOR of Two Numbers in Array Hard Bit Manipulation
• 1387. Maximum XOR Subarray (Prefix XOR + Trie) Hard Bit Manipulation
• 1388. Count Pairs with XOR in a Range Hard Bit Manipulation
• 1389. Maximum Genetic Difference Query Hard Bit Manipulation
• 1390. Sum of All XOR Triplets in Array Hard Bit Manipulation
• 1391. Find Subarray with Maximum XOR Hard Bit Manipulation
• 1392. Shortest Path in Binary Tree via XOR Hard Bit Manipulation
• 1393. Count Total Set Bits in All Numbers 1 to N Hard Bit Manipulation
• 1394. Find XOR Sum of All Pairs Bitwise AND Hard Bit Manipulation
• 1395. Count Pairs with AND Greater Than XOR Hard Bit Manipulation
• 1396. Longest Subarray with AND Greater Than Zero Hard Bit Manipulation
• 1397. Sum of XOR of All Subarrays Hard Bit Manipulation
• 1398. Count Subarrays with XOR Less Than K Hard Bit Manipulation
• 1399. Maximum AND of Two Numbers After One Swap Hard Bit Manipulation
• 1400. Find the Largest Number in Range with Max Set Bits Hard Bit Manipulation
• 1401. SOS DP — Sum Over Subsets Using Bitmask Hard Bit Manipulation
• 1402. Inclusion-Exclusion via Bitmask Hard Bit Manipulation
• 1403. Profile Dynamic Programming on Grid (Bitmask) Hard Bit Manipulation
• 1404. Broken Necklace — Bitmask Circular DP Hard Bit Manipulation
• 1405. 2-SAT Problem — Implication Graph + Bits Hard Bit Manipulation
• 1406. Fast Fourier Transform Butterfly — Bit Reversal Hard Bit Manipulation
• 1407. XOR Basis — Gaussian Elimination over GF(2) Hard Bit Manipulation
• 1408. Count Arrays with XOR Equal to K (Linear Basis) Hard Bit Manipulation
• 1409. Nim Game with Multiple Piles — Sprague-Grundy Hard Bit Manipulation
• 1410. Maximum Score from K Consecutive XOR Operations Hard Bit Manipulation