Easy Level

1. Segregate 0s and 1s in an array
2. C Program to Check if a Given String is Palindrome
3. C program to multiply two matrices
4. Calculate the angle between hour hand and minute hand
5. Count frequencies of all elements in array in O(1) extra space and O(n) time
6. Find the minimum distance between two numbers
7. Maximum sum such that no two elements are adjacent
8. Merge Sort
9. Program to Count numbers on fingers
10. Rearrange positive and negative numbers in O(n) time and O(1) extra space
11. Write an Efficient Function to Convert a Binary Tree into its Mirror Tree
12. Convert array into Zig-Zag fashion
13. Count all possible paths from top left to bottom right of a mXn matrix
14. Count all sub-arrays having sum divisible by k
15. Find duplicates in O(n) time and O(1) extra space | Set 1
16. Find Excel column name from a given column number
17. Find if there is a subarray with 0 sum
18. Find minimum number of coins that make a given value
19. Find the missing number in Arithmetic Progression
20. Find the row with maximum number of 1s
21. How to determine if a binary tree is height-balanced?
22. Largest subarray with equal number of 0s and 1s
23. Maximum sum such that no two elements are adjacent
24. Merge Sort for Linked Lists
25. Move all zeroes to end of array
26. Print a given matrix in spiral form
27. Print Left View of a Binary Tree
28. Recursively remove all adjacent duplicates
29. Reverse words in a given string
30. Search an element in a sorted and rotated array
31. Search in a row wise and column wise sorted matrix
32. Segregate Even and Odd numbers
33. Serialize and Deserialize a Binary Tree
34. Sort a linked list of 0s, 1s and 2s
35. Sort an array of 0s, 1s and 2s
36. Stack | Set 2 (Infix to Postfix)
37. Stock Buy Sell to Maximize Profit
38. Ugly Numbers
39. Write a function to reverse a linked list

Medium Level

1. Backtracking | Set 2 (Rat in a Maze)
2. Bottom View of a Binary Tree
3. How to print maximum number of ‘A’ using given four keys
4. Dynamic Programming | Set 7 (Coin Change)
5. Find Excel column name from a given column number
6. Find the number of islands | Set 1 (Using DFS)
7. Flattening a Linked List
8. How to print maximum number of A’s using given four keys
9. Largest Rectangular Area in a Histogram | Set 2
10. Minimum Number of Platforms Required for a Railway/Bus Station
11. Print Nodes in Top View of Binary Tree
12. Reverse a Linked List in groups of given size
13. Sort an array in wave form

Hard Level

1. Arrange given numbers to form the biggest number | Set 1
2. Arrange given numbers to form the biggest number