Top 100 Most Liked Data Structures and Algorithms Problems

1. Find a pair with the given sum in an arrayEasy
2. Longest Common Subsequence ProblemMedium
3. Deletion from BST (Binary Search Tree)Medium
4. Level order traversal of a binary treeEasy
5. Insertion in a BSTEasy
6. Tree Traversals – Inorder, Preorder, and PostorderMedium
7. 0–1 Knapsack ProblemMedium
8. Longest Increasing Subsequence using Dynamic ProgrammingHard
9. Subset Sum Problem – Dynamic Programming SolutionMedium
10. Longest Palindromic Subsequence using Dynamic ProgrammingMedium
11. Matrix Chain Multiplication using Dynamic ProgrammingHard
12. Print all subarrays with 0 sumMedium
13. Longest Common Substring ProblemMedium
14. Find the shortest path in a mazeMedium
15. Find subarrays with a given sum in an arrayMedium
16. Check if two binary trees are identical or notEasy
17. Rod Cutting ProblemMedium
18. Find the first or last occurrence of a given number in a sorted arrayEasy
19. Construct a binary tree from inorder and preorder traversalHard
20. Word Break Problem – Dynamic ProgrammingHard
21. Find all possible palindromic substrings of a stringHard
22. Count number of islandsMedium
23. The Levenshtein distance (Edit distance) ProblemMedium
24. Inversion count of an arrayHard
25. Chess Knight Problem | Find the shortest path from source to destinationHard
26. Partition Problem using Dynamic ProgrammingMedium
27. Check if a subarray with 0 sum exists or notMedium
28. Find the largest number possible from a given set of numbersMedium
29. Change all elements of row i and column j in a matrix to 0 if cell (i, j) is 0Medium
30. Find k’th smallest element in an arrayMedium
31. Determine whether a given binary tree is a BST or notMedium
32. Minimum Sum Partition ProblemHard
33. Build a Binary Search Tree from a preorder sequenceHard
34. Find the maximum difference between two array elements that satisfies the given constraintsMedium
35. Sort binary array in linear timeEasy
36. Snake and Ladder ProblemHard
37. Merge two sorted linked lists into oneMedium
38. Find the duplicate element in a limited range arrayMedium
39. Find k’th largest element in an arrayMedium
40. Find the shortest path from source to destination in a matrix that satisfies given constraintsHard
41. Find the largest subarray formed by consecutive integersMedium
42. Find the total number of unique paths in a maze from source to destinationMedium
43. Find maximum length subarray having a given sumMedium
44. Sort an array of 0’s, 1’s, and 2’s (Dutch National Flag Problem)Medium
45. Find the missing number in an array without using any extra spaceEasy
46. Find maximum length subarray having an equal number of 0’s and 1’sMedium
47. Find the diameter of a binary treeMedium
48. Find the maximum product of two integers in an arrayEasy
49. Longest Palindromic Substring ProblemMedium
50. Move all zeros present in an array to the endEasy
51. Print all possible Knight’s tours on a chessboardHard
52. Search a given key in BSTEasy
53. Find maximum sum submatrix present in a matrixMedium
54. Print matrix in spiral orderMedium
55. Find the size of the largest square submatrix of 1’s present in a binary matrixMedium
56. Find the Lowest Common Ancestor (LCA) of two nodes in a binary treeMedium
57. Job Sequencing Problem with DeadlinesMedium
58. Print all possible solutions to N–Queens problemHard
59. Rearrange linked list in increasing order (Sort linked list)Medium
60. Check if a linked list is palindrome or notMedium
61. In-place merge two sorted arraysMedium
62. Count occurrences of a number in a sorted array with duplicatesMedium
63. Find maximum cost path in a graph from a given source to a given destinationMedium
64. Print top view of a binary treeMedium
65. Find all possible combinations of words formed from the mobile keypadHard
66. Check if an undirected graph contains a cycle or notMedium
67. Find all distinct combinations of a given lengthMedium
68. Find minimum cost to reach the last cell of a matrix from its first cellMedium
69. Longest Repeated Subsequence ProblemMedium
70. Maximum Product Subarray ProblemHard
71. Compute the least cost path in a weighted digraph using BFSMedium
72. Find a triplet with the given sum in an arrayMedium
73. Evaluate a postfix expressionEasy
74. Shortest Common Supersequence ProblemMedium
75. Find the path between given vertices in a directed graphEasy
76. Print left view of a binary treeEasy
77. Maximum Sum Circular SubarrayHard
78. Rearrange an array with alternate high and low elementsMedium
79. Print all distinct subsets of a given setHard
80. Find maximum profit earned by buying and selling shares any number of timesMedium
81. Print all combinations of numbers from 1 to n having sum nMedium
82. Find inorder successor for the given key in a BSTMedium
83. Find k’th smallest and k’th largest element in a BSTEasy
84. Find the maximum sum of a subsequence with no adjacent elementsMedium
85. Right rotate an array k timesEasy
86. Maximum Subarray Sum using Divide and ConquerMedium
87. Find ancestors of a given node in a binary treeMedium
88. Find the number of rotations in a circularly sorted arrayEasy
89. K–Partition Problem | Printing all partitionsHard
90. 3–Partition ProblemMedium
91. Find the peak element in an arrayMedium
92. 4–Sum Problem | Quadruplets with a given sumMedium
93. Insert a node to its correct sorted position in a sorted linked listEasy
94. Print bottom view of a binary treeMedium
95. Find the minimum number of deletions required to convert a string into a palindromeMedium
96. Build a binary tree from a parent arrayHard
97. Wildcard Pattern MatchingHard
98. Bipartite GraphMedium
99. Spiral order traversal of a binary treeMedium
100. Check if a binary tree is a complete binary tree or notMedium

 
Also See:

Top 25 Algorithms Every Programmer Should Know

Top 50 Classic Data Structures Problems