Easy Level

1. Find if two rectangles overlap
2. Check if a given Binary Tree is SumTree
3. Check if two arrays are equal or not
4. Merge Sort
5. Queue | Set 1 (Introduction and Array Implementation)
6. QuickSort
7. Ugly Numbers
8. Find Excel column name from a given column number
9. Given a string, find its first non-repeating character
10. Given only a pointer/reference to a node to be deleted in a singly lin
11. How to determine if a binary tree is height-balanced?
12. Implement Queue using Stacks
13. Reverse words in a given string
14. Sort a stack using recursion
15. Stock Buy Sell to Maximize Profit

Medium Level

1. Count Possible Decodings of a given Digit Sequence
2. Dynamic Programming | Set 11 (Egg Dropping Puzzle)
3. Flattening a Linked List
4. Quickhull Algorithm for Convex Hull
5. Sort an array in wave form
6. Write a function to get the intersection point of two Linked Lists.

Hard Level

1. Implement LRU Cache