Recursion problems

178 Recursion DSA practice problems on CampusCode, each with statement, examples and constraints.

• 313. Print Linked List in Reverse (Recursive) Easy Linked List
• 324. Add 1 to a Number Represented as Linked List Easy Linked List
• 327. Reverse a Linked List Recursively Easy Linked List
• 354. Identical Linked Lists Check (Recursive) Easy Linked List
• 356. Reverse Linked List in Groups of K Medium Linked List
• 371. Pairwise Swap of Nodes Medium Linked List
• 391. Merge Two Sorted Lists — Recursive Approach Medium Linked List
• 392. Reverse Alternate K Nodes Medium Linked List
• 398. Reverse Linked List in K-Groups (Reverse Remaining Too) Hard Linked List
• 403. Josephus Problem Using Circular Linked List Hard Linked List
• 568. Reverse a Stack Using Recursion Easy Stack
• 569. Sort a Stack Using Recursion Easy Stack
• 571. Delete Middle Element of Stack Easy Stack
• 687. Print 1 to N Using Recursion Easy Recursion
• 688. Print N to 1 Using Recursion Easy Recursion
• 689. Factorial of a Number Easy Recursion
• 690. Nth Fibonacci Number Easy Recursion
• 691. Sum of First N Natural Numbers Easy Recursion
• 692. Product of First N Natural Numbers Easy Recursion
• 693. Power of a Number (x^n) Easy Recursion
• 694. Sum of Digits of a Number Easy Recursion
• 695. Reverse a String Using Recursion Easy Recursion
• 696. Check Palindrome Using Recursion Easy Recursion
• 697. Count Zeros in a Number Easy Recursion
• 698. GCD of Two Numbers (Euclidean Algorithm) Easy Recursion
• 699. LCM of Two Numbers Using Recursion Easy Recursion
• 700. Find Maximum Element in Array Recursively Easy Recursion
• 701. Find Minimum Element in Array Recursively Easy Recursion
• 702. Binary Search Using Recursion Easy Recursion
• 703. Linear Search Using Recursion Easy Recursion
• 704. Count Occurrences of Element in Array Easy Recursion
• 705. Reverse an Array Using Recursion Easy Recursion
• 706. Check if Array is Sorted (Recursive) Easy Recursion
• 707. Sum of Array Elements Using Recursion Easy Recursion
• 708. Print All Elements of Array Recursively Easy Recursion
• 709. Find Index of an Element Recursively Easy Recursion
• 710. Count Digits in a Number Easy Recursion
• 711. Multiply Two Numbers Without * Operator Easy Recursion
• 712. Print Multiplication Table Using Recursion Easy Recursion
• 713. Tower of Hanoi — Minimum Moves (Modulo 10^9+7) Easy Recursion
• 714. Print All Even Numbers up to N Easy Recursion
• 715. Print All Odd Numbers up to N Easy Recursion
• 716. Sum of Even Numbers up to N Easy Recursion
• 717. Recursive Bubble Sort Easy Recursion
• 718. Recursive Insertion Sort Easy Recursion
• 719. Print Fibonacci Series up to N Terms Easy Recursion
• 720. Check if a Number is a Power of 2 Easy Recursion
• 721. Check if a Number is a Power of 3 Easy Recursion
• 722. Flatten a Nested Array Recursively Easy Recursion
• 723. Recursive String Length Easy Recursion
• 724. Count Vowels in a String Recursively Easy Recursion
• 725. Remove All Occurrences of a Character Recursively Easy Recursion
• 726. Replace Spaces with Underscores (Recursive) Easy Recursion
• 727. Concatenate N Copies of a String Easy Recursion
• 728. Is Uppercase String (Recursive Check) Easy Recursion
• 729. Convert Number to Binary Using Recursion Easy Recursion
• 730. Convert Binary to Decimal Using Recursion Easy Recursion
• 731. Nth Row of Pascal's Triangle (Modulo 10^9+7) Easy Recursion
• 732. Recursive Exponentiation (Fast Power, Modulo 10^9+7) Easy Recursion
• 733. First Occurrence of Element in Array Easy Recursion
• 734. Last Occurrence of Element in Array Easy Recursion
• 735. Move All Zeros to End (Recursive) Easy Recursion
• 736. Single Entry of Pascal's Triangle — C(n, k) (Modulo 10^9+7) Easy Recursion
• 737. Recursive Floor Division Easy Recursion
• 738. Jump Search Using Recursion Easy Recursion
• 739. Print Pattern — Right Angle Triangle (Recursive) Easy Recursion
• 740. Print Pattern — Inverted Triangle (Recursive) Easy Recursion
• 741. Check Armstrong Number Recursively Easy Recursion
• 742. Sum of Squares of First N Numbers Easy Recursion
• 743. Recursive Palindrome Number Check Easy Recursion
• 744. Compute Binomial Coefficient C(n, r) (Modulo 10^9+7) Easy Recursion
• 745. Return All Indices of Target in Array Easy Recursion
• 746. Find the Sorted Position of Element (Recursive) Easy Recursion
• 747. Tribonacci Number Easy Recursion
• 748. Digital Root (Recursive Digit Sum) Easy Recursion
• 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
• 809. Stickers to Spell Word (Recursive + Memo) Hard Recursion
• 810. Reconstruct Itinerary — Euler Path Exists from JFK Hard Recursion
• 811. Shortest Path Visiting All Nodes (Recursion + Bitmask) Hard Recursion
• 812. 24 Game (All Expressions with 4 Numbers) 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
• 818. Number of Squareful Arrays 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
• 830. Count Special Subsequences (Mod 10^9+7) 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
• 839. Height / Maximum Depth of Binary Tree Easy Trees
• 841. Count Total Nodes in Binary Tree Easy Trees
• 842. Count Leaf Nodes Easy Trees
• 843. Sum of All Nodes Easy Trees
• 844. Check if Two Trees are Identical Easy Trees
• 845. Mirror / Invert a Binary Tree Easy Trees
• 846. Check if Binary Tree is Symmetric Easy Trees
• 847. Check if Binary Tree is Balanced Easy Trees
• 848. Diameter of Binary Tree Easy Trees
• 849. Maximum Path Sum Root to Leaf Easy Trees
• 850. Check if Path with Given Sum Exists Easy Trees
• 860. Check if Binary Tree is Full Easy Trees
• 861. Check if Binary Tree is Perfect Easy Trees
• 868. Convert Binary Tree to its Mirror Easy Trees
• 869. Sum of Nodes on Longest Path Root to Leaf Easy Trees
• 870. Count Half Nodes in Binary Tree Easy Trees
• 913. Check if Two Trees are Isomorphic Medium Trees