Merge problems

8 Merge DSA practice problems on CampusCode, each with statement, examples and constraints.

• 309. Merge Two Sorted Linked Lists Easy Linked List
• 355. Merge K Sorted Linked Lists Medium Linked List
• 391. Merge Two Sorted Lists — Recursive Approach Medium Linked List
• 394. Merge K Sorted Lists (Optimal — Min Heap) Hard Linked List
• 404. Merge M Sorted Lists of Variable Size Hard Linked List
• 923. Merge Two BSTs Medium Trees
• 1298. Merge Bits from Two Values at a Mask Easy Bit Manipulation
• 1314. Copy Set Bits of a Number in Another Easy Bit Manipulation