LeetCode Blind 75 Challenges with Solutions

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Blind 75 is a curated list of LeetCode questions created in 2018. We can practice these questions to save time in the job-finding process. Many other LeetCode problems are technical mixes of these individual problems.

Grind 75 is a dynamic list of top LeetCode interview questions created in 2023. It's up-to-date and well-chosen, and we can personalize it according to our schedule, time constraints, and preferences. I practice Grind 75 in parallel on this repository.

Goal: To achieve the review of the application of the following data structures and algorithms, except the theory of NP-Completeness.

• Data Structures: (1) Arrays; (2) Stacks and Queues; (3) Linked Lists; (4) Trees; (5) Graphs; (6) Sorting; (7) Hashing.
• Algorithms: (1) Greedy Method; (2) Divide and Conquer; (3) Tree Searching Strategies; (4) Prune and Search; (5) Dynamic Programming.

Recommended online textbook for quick review of concepts: Hello Algo

Project Timeline

• Start Date: Mar 26, 2023
• Completion Date: Ongoing 🧙🪄

1. Array

• Easy 1. Two Sum (picked in Grind 75)
• Easy 121. Best Time to Buy and Sell Stock (picked in Grind 75)
• Easy 217. Contains Duplicate (picked in Grind 75)
• Medium 11. Container With Most Water (picked in Grind 75) | Algo: Two-Pointer Technique
• Medium 15. 3Sum (picked in Grind 75) | Algo: Two-Pointer Technique and Dictionary (Hashmap); DS: Hashing
• Medium 33. Search in Rotated Sorted Array (picked in Grind 75) | Algo: Binary Search Algorithm, which follows the divide and conquer approach.
• Medium 53. Maximum Subarray (picked in Grind 75) | Algo: Kadane's Algo
• Medium 152. Maximum Product Subarray (picked in Grind 169) | Algo: Dynamic Programming
• Medium 153. Find Minimum in Rotated Sorted Array | Algo: Binary Search Algorithm, which follows the divide and conquer approach.
• Medium 238. Product of Array Except Self (picked in Grind 75)

2. Dynamic Programming

• Easy 70. Climbing Stairs (picked in Grind 75) | Algo: Dynamic Programming
• Medium 55. Jump Game
• Medium 62. Unique Paths (picked in Grind 75) | Algo: Dynamic Programming
• Medium 91. Decode Ways
• Medium 139. Word Break (picked in Grind 75) | Algo: Dynamic Programming
• Medium 198. House Robber (picked in Grind 169) | Algo: Dynamic Programming
• Medium 213. House Robber II
• Medium 300. Longest Increasing Subsequence (picked in Grind 169) | Algo: Dynamic Programming & Binary Search
• Medium 322. Coin Change (picked in Grind 75) | Algo: Dynamic Programming
• Medium 377. Combination Sum IV
• Medium 1143. Longest Common Subsequence

3. Graph

• Medium 128. Longest Consecutive Sequence
• Medium 133. Clone Graph (picked in Grind 75) | Algo: Breadth-First Search
• Medium 200. Number of Islands (picked in Grind 75) | Algo: Depth-First Search
• Medium 207. Course Schedule (picked in Grind 75) | Algo: Depth-First Search
• Medium 417. Pacific Atlantic Water Flow
• Alien Dictionary (Leetcode Premium)
• Graph Valid Tree (Leetcode Premium)
• Number of Connected Components in an Undirected Graph (Leetcode Premium)

4. Interval

• Medium 56. Merge Intervals (picked in Glind 75)
• Medium 57. Insert Interval (picked in Grind 75)
• Medium 435. Non-overlapping Intervals
• Meeting Rooms (Leetcode Premium)
• Meeting Rooms II (Leetcode Premium)

5. Linked List

• Easy 21. Merge Two Sorted Lists (picked in Grind 75)
• Easy 141. Detect Cycle in a Linked List (picked in Grind 75) | Algo: Floyd's Cycle Finding
• Easy 206. Reverse a Linked List (picked in Grind 75)
• Medium 19. Remove Nth Node From End Of List (picked in Grind 169) | Algo: Two-Pointers Technique (Fast & Slow Pointers)
• Medium 143. Reorder List
• Hard 23. Merge K Sorted Lists (picked in Grind 75) | DS: Min Heap (Priority Queue)

6. Matrix

• Medium 48. Rotate Image
• Medium 54. Spiral Matrix (picked in Grind 75)
• Medium 73. Set Matrix Zeroes
• Medium 79. Word Search (picked in Grind 75) | Algo: Depth-First Search

7. String

• Easy 20. Valid Parentheses (picked in Grind 75)
• Easy 125. Valid Palindrome (picked in Grind 75) | Algo: Regular Expressions, Two-Pointers Technique, String Manipulation
• Medium 3. Longest Substring Without Repeating Characters (picked in Grind 75) | Algo: Sliding Window Technique
• Medium 5. Longest Palindromic Substring (picked in Grind 75) | Algo: Expand Around Center & Two-Pointers Techniques
• Medium 49. Group Anagrams (picked in Grind 169) | DS: Hash Table
• Medium 242. Valid Anagram (picked in Grind 75)
• Medium 424. Longest Repeating Character Replacement
• Medium 647. Palindromic Substrings
• Hard 76. Minimum Window Substring (picked in Grind 75) | Algo: Sliding Window; DS: Hash Table
• Encode and Decode Strings (Leetcode Premium)

8. Tree

• Easy 100. Same Tree
• Easy 104. Maximum Depth of Binary Tree (picked in Grind 75) | Algo: Depth-First Search
• Easy 226. Invert/Flip Binary Tree (picked in Grind 75)
• Easy 572. Subtree of Another Tree (picked in Grind 169) | Algo: Depth-First Search
• Medium 98. Validate Binary Search Tree (picked in Grind 75) | Algo: Depth-First Search
• Medium 102. Binary Tree Level Order Traversal (picked in Grind 75) | Algo: Breadth-First Search
• Medium 105. Construct Binary Tree from Preorder and Inorder Traversal (picked in Grind 75) | Algo: Preorder & Inorder Traversal
• Medium 211. Design Add and Search Words Data Structure (picked in Grind 169) | DS: Trie Tree
• Medium 230. Kth Smallest Element in a BST (picked in Grind 75) | Algo: Inorder Traversal
• Medium 235. Lowest Common Ancestor of BST (picked in Grind 75)
• Hard 124. Binary Tree Maximum Path Sum
• Hard 212. Word Search II
• Hard 297. Serialize and Deserialize Binary Tree (picked in Grind 75) | Algo: Breadth-First Search; DS: Queue

9. Heap

• Medium 347. Top K Frequent Elements
• Hard 23. Merge K Sorted Lists (picked in Grind 75) | DS: Min Heap (Priority Queue)
• Hard 295. Find Median from Data Stream (picked in Grind 75) | DS: Min & Max Heaps (Priority Queue)

10. Bonus: Binary

• Easy 190. Reverse Bits (picked in Grind 169) | Algo: Bit Manipulation
• Easy 191. Number of 1 Bits (picked in Grind 169) | Algo: Bit Manipulation
• Easy 268. Missing Number (picked in Grind 169) | Algo: Bit Manipulation (XOR)
• Easy 338. Counting Bits (picked in Grind 169) | Algo: Dynamic Programming (Bit Manipulation)
• Medium 371. Sum of Two Integers