Top 100 DSA Interview Questions (Topic-wise)

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1. Arrays

1. Check if pair with the given Sum exists in Array - 🟢 Easy
2. Best Time to Buy and Sell Stock - 🟢 Easy
3. Find duplicates - 🟡 Medium
4. Product of Array Except Self - 🟡 Medium
5. Maximum Subarray - 🟢 Easy
6. Maximum Product Subarray - 🟡 Medium
7. Find Minimum in Rotated Sorted Array - 🟡 Medium
8. Search in Rotated Sorted Array - 🟡 Medium
9. 3 Sum - 🟡 Medium
10. Container With Most Water - 🟡 Medium
11. Trapping Rain Water - 🔴 Hard
12. Chocolate Distribution Problem - 🟢 Easy
13. Insert Interval - 🔴 Hard
14. Merge Intervals - 🟡 Medium
15. Non-overlapping Intervals - 🟡 Medium
16. Set Matrix Zeroes - 🟡 Medium
17. Spiral Matrix - 🟡 Medium
18. Program to find the transpose of a matrix - 🟢 Easy

2. Strings

19. Word Search - 🟡 Medium
20. Longest Substring Without Repeating Characters - 🟡 Medium
21. Longest Repeating Character Replacement - 🟡 Medium
22. Smallest window in a String containing all characters of another String - 🔴 Hard
23. Check whether two Strings are anagram of each other - 🟢 Easy
24. Print all anagrams together - 🟡 Medium
25. Check if given Parentheses expression is balanced or not - 🟢 Easy
26. Sentence Palindrome - 🟢 Easy
27. Longest Palindromic Substring - 🟡 Medium
28. Palindromic Substrings - 🟡 Medium
29. Longest Common Prefix - 🟢 Easy

3. Linked List

30. Reverse a Linked List - 🟢 Easy
31. Detect Cycle in a Linked List - 🟢 Easy
32. Merge Two Sorted Lists - 🟢 Easy
33. Merge K Sorted Lists - 🔴 Hard
34. Remove Nth Node From End Of List - 🟡 Medium
35. Reorder List - 🟡 Medium
36. Add 1 to a number represented as a linked list - 🟡 Medium
37. Find the middle of a given linked list - 🟢 Easy
38. Delete last occurrence of an item from a linked list - 🟡 Medium

4. Stacks and Queues

39. Valid Parentheses - 🟢 Easy
40. Convert Infix expression to Postfix expression - 🟡 Medium
41. Next Greater Element - 🟢 Easy
42. Delete middle element of a stack - 🟡 Medium

5. Trees

43. Check mirror in an n-ary tree - 🟢 Easy
44. The Celebrity Problem - 🟡 Medium
45. Length of the longest valid substring - 🔴 Hard
46. Print Right View of a Binary Tree - 🟡 Medium
47. Find the first circular tour that visits all petrol pumps - 🟡 Medium
48. Maximum Depth of Binary Tree - 🟢 Easy
49. Check if two trees have the same structure - 🟢 Easy
50. Invert/Flip Binary Tree - 🟢 Easy
51. Binary Tree Maximum Path Sum - 🔴 Hard
52. Binary Tree Level Order Traversal - 🟡 Medium
53. Serialize and Deserialize Binary Tree - 🔴 Hard
54. Subtree of Another Tree - 🟢 Easy
55. Construct Binary Tree from Preorder and Inorder Traversal - 🟡 Medium
56. Validate Binary Search Tree - 🟡 Medium
57. Kth Smallest Element in a BST - 🟡 Medium
58. Lowest Common Ancestor of BST - 🟢 Easy

6. Trie

59. Implement Trie (Prefix Tree) - 🟡 Medium
60. Add and Search Word - 🟡 Medium

7. Heap

61. Top K Frequent Elements - 🟡 Medium
62. Find Median from Data Stream - 🔴 Hard
63. Largest triplet product in a stream - 🟢 Easy
64. Connect n ropes with minimum cost - 🟡 Medium

8. Graphs

65. Clone Graph - 🟡 Medium
66. Course Schedule - 🟡 Medium
67. Pacific Atlantic Water Flow - 🟡 Medium
68. Number of Islands - 🟡 Medium
69. Longest Consecutive Sequence - 🔴 Hard
70. Snake and Ladder Problem - 🟡 Medium
71. Detect Cycle in a Directed Graph - 🟡 Medium
72. Bridges in a graph - 🔴 Hard
73. Check whether a given graph is Bipartite or not - 🟡 Medium
74. Find size of the largest region in a Boolean Matrix - 🟡 Medium
75. Flood fill Algorithm - 🟢 Easy
76. Strongly Connected Components - 🔴 Hard
77. Topological Sorting - 🟡 Medium

9. Dynamic Programming

78. Count ways to reach the n’th stair - 🟢 Easy
79. Coin Change - 🟡 Medium
80. 0/1 Knapsack Problem - 🟡 Medium
81. Longest Increasing Subsequence - 🟡 Medium
82. Longest Common Subsequence - 🟡 Medium
83. Word Break Problem - 🟡 Medium
84. Dice Throw - 🟡 Medium
85. Egg Dropping Puzzle - 🔴 Hard
86. Matrix Chain Multiplication - 🟡 Medium
87. Combination Sum - 🟡 Medium
88. Subset Sum Problem - 🟡 Medium
89. Find maximum possible stolen value from houses - 🟢 Easy
90. Count Possible Decodings of a given Digit Sequence - 🟡 Medium
91. Unique paths in a Grid with Obstacles - 🟡 Medium
92. Jump Game - 🟡 Medium
93. Cutting a Rod - 🟡 Medium
94. Maximum Product Cutting - 🟡 Medium
95. Count number of ways to cover a distance - 🟢 Easy

10. Bit Manipulation

96. Number of 1 Bits - 🟢 Easy
97. Counting Bits - 🟡 Medium
98. Missing Number - 🟢 Easy
99. Reverse Bits - 🟢 Easy
100. Find XOR of all subsets of a set - 🟡 Medium

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