75 Hard Challenge - Daily LeetCode Coding

Challenge Overview

🏆 75 Hard Challenge is a commitment to self-improvement and discipline. It consists of the following daily tasks:

• 💪 Workout: Engage in a daily physical workout to enhance your fitness.
• 📚 Reading/Coding: Solve one or two LeetCode questions from the top 150 interview questions. Sharpen your coding skills and problem-solving abilities.
• 💧 5 Liters of Water: Stay hydrated by consuming at least 5 liters of water throughout the day.
• 🍎 Follow a Diet: Stick to a balanced diet that aligns with your health goals.
• 📷 Take a Progress Photo: Capture your progress along the way. Visual documentation can be a motivating factor.
• 🧘 Meditation (At least 5 minutes): Dedicate time to meditation to enhance mindfulness and mental clarity.

Why LeetCode?

LeetCode offers a valuable platform for coding practice and problem-solving, especially for technical interviews. Consistent practice on LeetCode can improve your coding skills and boost your confidence.

Repository Structure

• Daily Coding: Store your daily LeetCode solutions here.
• Progress Photos: Maintain a visual record of your progress.

Stay Committed

Remember, the 75 Hard Challenge is about personal growth and discipline. Stay committed to your goals, and track your journey. You've got this!

Progress

In first attempt I solved questions for 21 days

Low Level Design

1. Design a Parking Lot
2. Google Calendar

Questions Solved (Attempt 1)

Array / String

• Day 1: 88. Merge Sorted Array
• Day 1: 151. Reverse Words in a String
• Day 2: 80 Remove Duplicates from Sorted Array II
• Day 3: 27. Remove Element
• Day 3: 88. Merge Sorted Array
• Day 4: 26. Remove Duplicates from Sorted Array
• Day 5: 169. Majority Element
• Day 5: 189. Rotate Array
• Day 6: 121. Best Time to Buy and Sell Stock
• Day 6: 2016. Maximum Difference Between Increasing Elements
• Day 7: 122. Best Time to Buy and Sell Stock II
• Day 8: 55. Jump Game
• Day 9: 45. Jump Game II
• Day 10: 274. H-Index
• Day 10: 275. H-Index II
• Day 10: 380. Insert Delete GetRandom O(1)
• Day 11: 238. Product of Array Except Self
• Day 12: 134. Gas Station
• Day 13: 13. Roman to Integer
• Day 14: 12. Integer to Roman
• Day 15: 58. Length of Last Word
• Day 15: 14. Longest Common Prefix
• Day 15: 6. Zigzag Conversion
• Day 16: 28. Find the Index of the First Occurrence in a String

Two Pointers

• Day 16: 125. Valid Palindrome
• Day 17: 392. Is Subsequence
• Day 17: 167. Two Sum II - Input Array Is Sorted
• Day 18: 11. Container With Most Water
• Day 19: 15. 3Sum

Sliding Window

• Day 19: 209. Minimum Size Subarray Sum
• Day 19: 3. Longest Substring Without Repeating Characters

Matrix

• Day 20: 36. Valid Sudoku
• Day 21: 54. Spiral Matrix

Question Solved (Attempt 2)

• Day 1: 48. Rotate Image
• Day 2: 73. Set Matrix Zeroes
• Day 3: 289. Game of Life

Hashmap

• Day 3: 383. Ransom Note
• Day 4: 205. Isomorphic Strings
• Day 5: [](No question)
• Day 6: 290. Word Pattern
• Day 6: 242. Valid Anagram
• Day 7: 49. Group Anagrams
• Day 7: 1. Two Sum
• Day 7: 202. Happy Number
• Day 8: 219. Contains Duplicate 11
• Day 9: 128. Longest Consecutive Sequence

After 15 days

Intervals

• Day 10: 228. Summary Ranges
• Day 10: 56. Merge Intervals
• Day 10: 57. Insert Interval
• Day 10: 452. Minimum Number of Arrows to Burst Balloons

Stack

• Day 10: 20. Valid Parentheses
• Day 10: 71. Simplify Path
• Day 11: 155. Min Stack
• Day 11: 150. Evaluate Reverse Polish Notation

Linked List

• Day 12: 141. Linked List Cycle
• Day 12: 2. Add Two Numbers
• Day 12: 21. Merge Two Sorted Lists
• Day 13: 138. Copy List with Random Pointer
• Day 14: 92. Reverse Linked List II
• Day 14: 206. Reverse Linked List
• Day 14: 19. Remove Nth Node From End of List
• Day 14: 82. Remove Duplicates from Sorted List II
• Day 15: 61. Rotate List
• Day 15: 86. Partition List
• Day 15: 146. LRU Cache

Binary Tree General

• Day 16: 104. Maximum Depth of Binary Tree
• Day 16: 226. Invert Binary Tree
• Day 16: 101. Symmetric Tree
• Day 17: 105. Construct Binary Tree from Preorder and Inorder Traversal
• Day 18: 106. Construct Binary Tree from Inorder and Postorder Traversal
• Day 19: 117. Populating Next Right Pointers in Each Node II
• Day 20: 114. Flatten Binary Tree to Linked List
• Day 20: 112. Path Sum

After 8 days

• Day 21: 129. Sum Root to Leaf Numbers
• Day 21: 222. Count Complete Tree Nodes
• Day 21: 236. Lowest Common Ancestor of a Binary Tree

Binary Tree BFS

• Day 21: 199. Binary Tree Right Side View
• Day 21: 637. Average of Levels in Binary Tree
• Day 21: 102. Binary Tree Level Order Traversal
• Day 21: 103. Binary Tree Zigzag Level Order Traversal

Binary Search Tree

• Day 21: 530. Minimum Absolute Difference in BST
• Day 21: 230. Kth Smallest Element in a BST
• Day 22: 98. Validate Binary Search Tree

Graph General

• Day 22: 200. Number of Islands
• Day 23: 130. Surrounded Regions
• Day 23: 133. Clone Graph

After 17 days

• Day 24: 399. Evaluate Division
• Day 24: 207. Course Schedule
• Day 24: 210. Course Schedule II

Trie

• Day 24: 208. Implement Trie (Prefix Tree)
• Day 24: 211. Design Add and Search Words Data Structure

After 17 days:

Backtracking

• Day 25: 17. Letter Combinations of a Phone Number
• Day 25: 77. Combinations
• Day 25: 46. Permutations
• Day 26: 39. Combination Sum
• Day 26: 22. Generate Parentheses
• Day 26: 79. Word Search

Divide & Conquer

• Day 27: 108. Convert Sorted Array to Binary Search Tree
• Day 28: 427. Construct Quad Tree
• Day 28: 148. Sort List

Kadane's Algorithm

• Day 29: 53. Maximum Subarray
• Day 29: 918. Maximum Sum Circular Subarray

Binary Search

• Day 29: 35. Search Insert Position
• Day 29: 74. Search a 2D Matrix
• Day 29: 33. Search in Rotated Sorted Array
• Day 30: 162. Find Peak Element
• Day 30: 34. Find First and Last Position of Element in Sorted Array
• Day 31: 153. Find Minimum in Rotated Sorted Array

Heap

• Day 31: 215. Kth Largest Element in an Array
• Day 31: 373. Find K Pairs with Smallest Sums
• Day 31: 295. Find Median from Data Stream

Bit Manipulation

• Day 32: 67. Add Binary
• Day 32: 190. Reverse Bits
• Day 32: 191. Number of 1 Bits
• Day 32: 136. Single Number
• Day 32: 137. Single Number II
• Day 32: 201. Bitwise AND of Numbers Range

MATH

• Day 32: 9. Palindrome Number
• Day 32: 66. Plus One
• Day 32: 172. Factorial Trailing Zeroes
• Day 32: 69. Sqrt(x)
• Day 32: 50. Pow(x, n)

1D DP

• Day 33: 70. Climbing Stairs
• Day 33: 198. House Robber
• Day 33: 139. Word Break
• Day 34: 322. Coin Change
• Day 34: 300. Longest Increasing Subsequence

Multidimensional DP

• Day 34: 120. Triangle
• Day 35: 64. Minimum Path Sum
• Day 36: 63. Unique Paths II
• Day 37: 5. Longest Palindromic Substring

Level: HARD Questions

• Day 38: 135. Candy
• Day 39: 42. Trapping Rain Water
• Day 39: 68. Text Justification
• Day 40: 30. Substring with Concatenation of All Words
• Day 40: 76. Minimum Window Substring
• Day 40: 224. Basic Calculator
• Day 40: 25. Reverse Nodes in k-Group
• Day 40: 127. Word Ladder
• Day 40: 212. Word Search II
• Day 40: 52. N-Queens II
• Day 40: 23. Merge k Sorted Lists
• Day 40: 4. Median of Two Sorted Arrays
• Day 40: 201. Bitwise AND of Numbers Range
• Day 40: 149. Max Points on a Line
• Day 40: 123. Best Time to Buy and Sell Stock III
• Day 40: 188. Best Time to Buy and Sell Stock IV