Coding Interview Questions

This Repository is aimed to help professional programmers/students improve problem solving and tackle basic concepts. The contents are based on questions that we have come across during our interview experiences.

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Heap Problems	Difficulty	solution link
Leetcode Problem 21. Merge Two Sorted Lists	Easy	python
Leetcode Problem 23 Merge K Sorted Lists	Medium	python
Leetcode Problem 295 Find Median from Data Stream	Hard	python
Leetcode Problem 692 Top K Frequent Words	Medium	python
Leetcode Problem 703 Kth Largest Element in a Stream	Easy	python
Leetcode Problem 973. K Closest Points to Origin	Medium	python

Binary Search Problems	Difficulty	solution link
Leetcode Problem 4 Median of two sorted arrays	Hard	CSharp
Leetcode Problem 33. Search in Rotated Sorted Array	Medium	Python
Leetcode Problem 34. Find First and Last Position of Element in Sorted Array	Medium	CSharp
Leetcode Problem 74. Search a 2D Matrix	Medium	python
Leetcode Problem 162 Find Peak Element	Medium	CSharp

Dynamic Programming Problems	Difficulty	solution link
Leetcode Problem 44 Wildcard Matching	Hard	Python
Leetcode Problem 55. Jump Game	Medium	python
Leetcode Problem 62 Unique Paths	Medium	Python
Leetcode Problem 63 Unique Paths	Medium	Python
Leetcode Problem 64. Minimum Path Sum	Medium	Python
Leetcode Problem 70. Climbing Stairs	Easy	Python
Leetcode Problem 72 Edit Distance	Hard	Python
Leetcode Problem 85. Maximal Rectangle	Hard	Python
Leetcode Problem 139. Word Break	Medium	Python
Leetcode Problem 140. Word Break II	Hard	Python
Leetcode Problem 198 House Robber	Easy	Python
Leetcode Problem 221. Maximal Square	Medium	Python
Leetcode Problem 322 Coin Change	Medium	Python
Leetcode Problem 348. Design Tic-Tac-Toe	Medium	Python
Leetcode Problem 1143. Longest Common Subsequence	Medium	Python

Linked List Problems	Difficulty	solution link
Leetcode Problem 2 Add Two Numbers	Medium	Python
Leetcode Problem 19. Remove Nth Node From End of List	Medium	Python
Leetcode Problem 24. Swap Nodes in Pairs	Medium	Python
Leetcode Problem 82 Remove Duplicates from sorted list	Medium	CSharp
Leetcode Problem 92. Reverse Linked List II	Medium	Python
Leetcode Problem 141. Linked List Cycle	Medium	CSharp
Leetcode Problem 142. Linked List Cycle 2	Medium	CSharp
Leetcode Problem 146. LRU Cache	Medium	Python

Backtracking Problems	Difficulty	solution link
Leetcode Problem 39. Combination Sum	Medium	CSharp
Leetcode Problem 51 N-Queens	Hard	CSharp
Leetcode Problem 72 Edit Distance	Hard	CSharp
Leetcode Problem 78. Subsets	Medium	Python

BFS DFS Problems	Difficulty	solution link
Leetcode Problem 79. Word Search	Medium	Python
Leetcode Problem 102. Binary Tree Level Order Traversal	Medium	Python
Leetcode Problem 103. Binary Tree Zigzag Level Order Traversal	Medium	Python
Leetcode Problem 130. Surrounded Regions	Medium	Python
Leetcode Problem 207 Course Schedule	Medium	Python
Leetcode Problem 210 Course Schedule II	Medium	Python
Leetcode Problem 289 Game of life	Medium	Python
Leetcode Problem 339 Nested List Weight Sum	Medium	Python
Leetcode Problem 472. Concatenated Words	Hard	Python
Leetcode Problem 529. Minesweeper	Medium	Python
Leetcode Problem 733. Flood Fill	Easy	Python
Leetcode Problem 994 Rotting Oranges	Easy	Python

Two Pointer Problems	Difficulty	solution link
Leetcode Problem 3 Longest Substring Without Repeating Characters	Medium	Python
Leetcode Problem 5 Longest Palindrome Substring	Medium	Python
Leetcode Problem 27 Remove Element	Easy	Python
Leetcode Problem 15 3Sum	Medium	Python
Leetcode Problem 26. Remove Duplicates from Sorted Array	Easy	Python
Leetcode Problem 45. Jump Game II	Medium
Leetcode Problem 58. Length of last character	Easy
Leetcode Problem 76. Minimum Window Substring	Hard	Python
Leetcode Problem 125 Valid Palindrome	Easy	Python
Leetcode Problem 209. Minimum Size Subarray Sum	Medium	Python
Leetcode Problem 392 Is Subsequence	Easy	Python
Leetcode Problem 408. Valid Word Abbreviation	Medium
Leetcode Problem 680 Valid Palindrome II	Easy	Python
Leetcode Problem 1650. Lowest Common Ancestor of a Binary Tree III	Medium
Leetcode Problem 2405. Optimal Partition of String	Easy

Recursion & Trees	Difficulty	solution link
Leetcode Problem 17. Letter Combinations of a Phone Number	Easy	Csharp
Leetcode Problem 22. Generate Parentheses	Easy	Csharp
Leetcode Problem 46. Permutations	Medium	Python
Leetcode Problem 94. Binary Tree Inorder Traversal	Medium	Python
Leetcode Problem 98. Validate Binary Search Tree	Medium	Python
Leetcode Problem 100. Same Tree	Easy	Python
Leetcode Problem 101. Symmetric Tree	Easy	CSharp
Leetcode Problem 104. Maximum Depth of Binary Tree	Easy	Python
Leetcode Problem 105. Construct Binary Tree from Preorder and Inorder Traversal	Medium	Python
Leetcode Problem 108. Convert Sorted Array to Binary Search Tree	Easy	Python
Leetcode Problem 110. Balanced Binary Tree	Easy	Python
Leetcode Problem 111. Minimum Depth of Binary Tree	Easy	Python
Leetcode Problem 112. Path Sum	Easy	Python
Leetcode Problem 113. Path Sum II	Easy	Python
Leetcode Problem 114. Flatten Binary Tree	Medium	Python
Leetcode Problem 124. Binary Tree Maximum Path Sum	Easy	Python
Leetcode Problem 297. Serialize and Deserialize Binary Tree	Hard	Python
Leetcode Problem 1367. Linked List in Binary Tree	Medium	Python

Random Algorithm	Difficulty	solution link
Leetcode Problem 7 Reverse Integer	Easy	Python
Leetcode Problem 9. Palindrome Number	Easy	Python
Leetcode Problem 13 Roman to Integer	Easy	Csharp
Leetcode Problem 36. Valid Sudoku	Medium	Python
Leetcode Problem 41. First Missing Positive	Hard	Python
Leetcode Problem 42. Trapping Rain Water	Hard	Python
Leetcode Problem 53. Maximum Subarray	Easy	Python
Leetcode Problem 54. Spiral Matrix	Medium	Python
Leetcode Problem 59. Spiral Matrix II	Medium	Python
Leetcode Problem 66. Plus One	Medium	Python
Leetcode Problem 73. Set Matrix Zeroes	Medium	Python
Leetcode Problem 121. Best Time to Buy and Sell Stock	Easy	Python
Leetcode Problem 190. Reverse Bits	Easy	Python
Leetcode Problem 268 Missing Number	Easy	Python
Leetcode Problem 277. Find the Celebrity	Medium	Python
Leetcode Problem 334. Increasing Triplet Subsequence	Medium	Python
Leetcode Problem 344. Reverse String	Easy	Python
Leetcode Problem 384. Shuffle an Array	Medium	Python
Leetcode Problem 415. Add Strings	Easy	Python
Leetcode Problem 1480 running sum of 1d array	Easy	Python

Trie Algorithm Based	Difficulty	solution link
Leetcode Problem 208. Implement Trie (Prefix Tree)	Medium	Python
Leetcode Problem 212. Word Search II	Medium	Python
Leetcode Problem 1233. Remove Sub-Folders from the Filesystem	Medium	Python

Hash maps and Arrays	Difficulty	solution link
Leetcode Problem 1. Two Sum	Easy	Python
Leetcode Problem 128. Longest Consecutive Sequence	Medium	Csharp
Leetcode Problem 138. Copy List with Random Pointer	Medium	Python
Leetcode Problem 290. Word Pattern	Easy	Python
Leetcode Problem 340. Longest Substring with At Most K Distinct Characters	Hard	[Python]
Leetcode Problem 454. 4Sum II	Medium	Python

Sort	Difficulty	solution link
Leetcode Problem 75. Sort Colors	Medium	Python
Leetcode Problem 80. Remove duplicates from sorted arrary II	Medium	Python
Leetcode Problem 88. Merge Sorted Array	Medium	Python
Leetcode Problem 179. Largest Number	Medium	Python
Leetcode Problem 148. Sort List	Medium	Python
Leetcode Problem 253. Meeting Rooms II	Medium	[Python]
Leetcode Problem 315. Count of Smaller Numbers After Self	Hard	Python
Leetcode Problem 324. Wiggle Sort II	Medium	Python

Stack Problems	Difficulty	solution link
Leetcode Problem 20. Valid Parentheses	Easy
Leetcode Problem 224. Basic calculator	Hard	Python
Leetcode Problem 341. Flatten Nested List Iterator	Medium	Python
Leetcode Problem 1249. Minimum Remove to Make Valid Parentheses	Medium

Math Problems	Difficulty	solution link
Leetcode Problem 74. Search a 2D Matrix	Medium	Python
Leetcode Problem 118. Pascal's Triangle	Easy	Python
Leetcode Problem 326. Power of Three	Easy	Python
Leetcode Problem 1362. Closest Divisors	Medium	Python
Leetcode Problem 1363. Largest Multiple of Three	Hard	Python

Bit manipulation Problems	Difficulty	solution link
Leetcode Problem 67. Add binary	Easy	Python