As the placement season is back so are we to help you ace the interview. We have selected some most commonly asked and must do practice problems for you.

You can also take part in our mock placement contests which will help you learn different topics and practice at the same time, simulating the feeling of a real placement test environment.

**Note : **Now you can track your progress of these questions Must Do Interview Preparation Course.

Topic :

• Arrays
• String
• Linked List
• Stack and Queue
• Tree and BST
• Heap
• Recursion
• Hashing
• Graph
• Greedy
• Dynamic Programming
• Divide and Conquer
• Backtracking
• Bit Magic

Arrays :

1. Subarray with given sum
2. Count the triplets
3. Kadane’s Algorithm
4. Missing number in array
5. Merge two sorted arrays
6. Rearrange array alternatively
7. Number of pairs
8. Inversion of Array
9. Sort an array of 0s, 1s and 2s
10. Equilibrium point
11. Leaders in an array
12. Minimum Platforms
13. Reverse array in groups
14. K’th smallest element
15. Trapping Rain Water
16. Pythagorean Triplet
17. Chocolate Distribution Problem
18. Stock buy and sell
19. Element with left side smaller and right side greater
20. Convert array into Zig-Zag fashion
21. Last Index of 1
22. Spirally traversing a matrix
23. Largest Number formed from an Array

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String :

1. Reverse words in a given string
2. Permutations of a given string
3. Longest Palindrome in a String
4. Recursively remove all adjacent duplicates
5. Check if string is rotated by two places
6. Roman Number to Integer
7. Anagram
8. Remove Duplicates
9. Form a Palindrome
10. Longest Distinct Characters in the string
11. Implement Atoi
12. Implement strstr
13. Longest Common Prefix

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Linked List :

1. Finding middle element in a linked list
2. Reverse a linked list
3. Rotate a Linked List
4. Reverse a Linked List in groups of given size
5. Intersection point in Y shaped linked lists
6. Detect Loop in linked list
7. Remove loop in Linked List
8. n’th node from end of linked list
9. Flattening a Linked List
10. Merge two sorted linked lists
11. Intersection point of two Linked Lists
12. Pairwise swap of a linked list
13. Add two numbers represented by linked lists
14. Check if Linked List is Palindrome
15. Implement Queue using Linked List
16. Implement Stack using Linked List
17. Given a linked list of 0s, 1s and 2s, sort it
18. Delete without head pointer

Stack and Queue :

1. Parenthesis Checker
2. Next larger element
3. Queue using two Stacks
4. Stack using two queues
5. Get minimum element from stack
6. LRU Cache
7. Circular tour
8. First non-repeating character in a stream
9. Rotten Oranges
10. Maximum of all subarrays of size k

Tree :

1. Print Left View of Binary Tree
2. Check for BST
3. Print Bottom View of Binary Tree
4. Print a Binary Tree in Vertical Order
5. Level order traversal in spiral form
6. Connect Nodes at Same Level
7. Lowest Common Ancestor in a BST
8. Convert a given Binary Tree to Doubly Linked List
9. Write Code to Determine if Two Trees are Identical or Not
10. Given a binary tree, check whether it is a mirror of itself
11. Height of Binary Tree
12. Maximum Path Sum
13. Diameter of a Binary Tree
14. Number of leaf nodes
15. Check if given Binary Tree is Height Balanced or Not
16. Serialize and Deserialize a Binary Tree

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Heap :

1. Find median in a stream
2. Heap Sort
3. Operations on Binary Min Heap
4. Rearrange characters
5. Kth largest element in a stream
6. Merge K sorted linked lists
7. Kth largest element in a stream

Recursion :

1. Flood fill Algorithm
2. Number of paths
3. Combination Sum – Part 2
4. Special Keyboard
5. Josephus problem

Hashing :

1. Relative Sorting
2. Sorting Elements of an Array by Frequency
3. Largest subarray with 0 sum
4. Common elements
5. Find all four sum numbers
6. Swapping pairs make sum equal
7. Count distinct elements in every window
8. Array Pair Sum Divisibility Problem
9. Longest consecutive subsequence
10. Array Subset of another array
11. Find all pairs with a given sum
12. Find first repeated character
13. Zero Sum Subarrays
14. Minimum indexed character
15. Check if two arrays are equal or not
16. Uncommon characters
17. Smallest window in a string containing all the characters of another string
18. First element to occur k times
19. Check if frequencies can be equal

Graph :

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