Data Structures

• [WIP] Associative Arrays
• [WIP] Trees

Coding Patterns

Arrays

Two Pointers

K-Sum Problems

1. Easy: 1. Two Sum
2. Medium: 167. Two Sum II - Input Array Is Sorted
3. Medium: 15. 3Sum
4. Medium: 16. 3Sum Closest
5. Medium: 259. 3Sum Smaller
6. Medium: 1679. Max Number of K-Sum Pairs
7. Medium: 532. K-diff Pairs in an Array

Palindrome Problems

8. Easy: 9. Palindrome Number
9. Easy: 125. Valid Palindrome
10. Easy: 680. Valid Palindrome II

Miscellaneous Problems

11. Easy: 283. Move Zeroes
12. Easy: 392. Is Subsequence
13. Easy: 977. Squares of a Sorted Array
14. Medium: 11. Container with Most Water
15. Medium: 75. Sort Colors
16. Medium: 151. Reverse Words in a String
17. Medium: 1438. Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit

Fast and Slow Pointers

1. Easy: 141. Linked List Cycle
2. Easy: 202. Happy Number
3. Easy: 234. Palindrome Linked List
4. Medium: 457. Circular Array Loop
5. Easy: 876. Middle of the Linked List

Sliding Window

1. Easy: 121. Best Time to Buy and Sell Stock
2. Easy: 643. Maximum Average Subarray I
3. Medium: 3. Longest Substring Without Repeating Characters
4. Medium: 187. Repeated DNA Sequences
5. Medium: 209. Minimum Size Subarray Sum
6. Medium: 340. Longest Substring with At Most K Distinct Characters
7. Medium: 395. Longest Substring with At Least K Repeating Characters
8. Medium: 487. Max Consecutive Ones II
9. Medium: 904. Fruit into Baskets
10. Medium: 1004. Max Consecutive Ones III
11. Medium: 1248. Count Number of Nice Subarrays
12. Medium: 1456. Maximum Number of Vowels in a Substring of Given Length
13. Medium: 1493. Longest Subarray of 1’s After Deleting One Element
14. Hard: 30. Substring with Concatenation of All Words
15. Hard: 76. Minimum Window Substring
16. Hard: 239. Sliding Window Maximum
17. Hard: 727. Minimum Window Subsequence

Merge Intervals

1. Easy: 228. Summary Ranges
2. Easy: 252. Meeting Rooms
3. Easy: 2446. Determine if Two Events Have Conflict
4. Medium: 56. Merge Intervals (Amberflo)
5. Medium: 57. Insert Interval
6. Medium: 253. Meeting Rooms II
7. Medium: 435. Non-overlapping Intervals (Amberflo.io)
8. Medium: 452. Minimum Number of Arrows to Burst Balloons
9. Medium: 986. Interval List Intersections (H2O.ai)
10. Medium: 1094. Car Pooling
11. Medium: 2406. Divide Intervals Into Minimum Number of Groups
12. Medium: 2410. Maximum Matching of Players with Trainers
13. Medium: 2462. Total Cost to Hire K Workers
14. Hard: 759. Employee Free Time
15. Hard: 2158. Amount of New Area Painted Each Day
16. Hard: 2213. Longest Substring of One Repeating Character
17. Hard: 2251. Number of Flowers in Full Bloom
18. Hard: 2276. Count Integers in Intervals
19. Hard: 2402. Meeting Rooms III

K-way Merge

1. Easy: 88. Merge Sorted Array
2. Medium: 373. Find K Pairs with Smallest Sums
3. Medium: 378. Kth Smallest Element in a Sorted Matrix
4. Hard: 4. Median of Two Sorted Arrays
5. Hard: 23. Merge k Sorted Lists

Miscellaneous

1. Easy: 1351. Count Negative Numbers in a Sorted Matrix

Backtracking

1. Medium: 46. Permutations
2. Medium: 47. Permutations II
3. Medium: 31. Next Permutation
4. Medium: 78. Subsets
5. Medium: 90. Subsets II
6. Medium: 39. Combination Sum
7. Medium: 40. Combination Sum II
8. Medium: 216. Combination Sum III
9. Medium: 131. Palindrome Partitioning
10. Hard: 132. Palindrome Partitioning II
11. Hard: 51. N-Queens
12. Hard: 52. N-Queens II
13. Medium: 17. Letter Combinations of a Phone Number
14. Medium: 22. Generate Parentheses
15. Medium: 77. Combinations
16. Medium: 79. Word Search
17. Medium: 93. Restore IP Addresses
18. Medium: 241. Different Ways to Add Parentheses
19. Medium: 320. Generalized Abbreviation
20. Medium: 473. Matchsticks to Square
21. Medium: 490. The Maze
22. Medium: 494. Target Sum
23. Medium: 526. Beautiful Arrangement
24. Medium: 638. Shopping Offers
25. Medium: 784. Letter Case Permutation
26. Medium: 797. All Paths From Source to Target
27. Medium: 1219. Path with Maximum Gold
28. Hard: 37. Sudoku Solver
29. Hard: 282. Expression Add Operators
30. Hard: 301. Remove Invalid Parentheses
31. Hard: 425. Word Squares
32. Hard: 489. Robot Room Cleaner

Custom Data Structures

1. Easy: 359. Logger Rate Limiter

Bit Manipulation

1. Easy: 136. Single Number
2. Easy: 190. Reverse Bits
3. Easy: 191. Number of 1 Bits
4. Easy: 231. Power of Two
5. Easy: 268. Missing Number
6. Easy: 338. Counting Bits
7. Easy: 389. Find the Difference
8. Easy: 461. Hamming Distance
9. Easy: 476. Number Complement
10. Easy: 832. Flipping an Image
11. Medium: 137. Single Number II
12. Medium: 201. Bitwise AND of Numbers Range
13. Medium: 371. Sum of Two Integers
14. Medium: 477. Total Hamming Distance
15. Medium: 1318. Minimum Flips to Make a OR b Equal to c

Modified Binary Search

Search in Array

1. Easy: 35. Search Insert Position
2. Easy: 744. Find Smallest Letter Greater Than Target
3. Medium: 34. Find First and Last Position of Element in Sorted Array

Standard Search

1. Easy: 278. First Bad Version
2. Easy: 374. Guess Number Higher or Lower
3. Medium: 74. Search a 2D Matrix
4. Medium: 702. Search in a Sorted Array of Unknown Size

Math

1. Easy: 69. Sqrt(x)
2. Easy: 367. Valid Perfect Square
3. Easy: 441. Arranging Coins

Tricky Invariant

1. Medium: 275. H-Index II
2. Medium: 540. Single Element in a Sorted Array
3. Medium: 658. Find K Closest Elements
4. Medium: 852. Peak Index in a Mountain Array

As a Tool

1. Easy: 1099. Two Sum Less Than K
2. Medium: 300. Longest Increasing Subsequence
3. Medium: 1498. Number of Subsequences That Satisfy the Given Sum Condition

On Solution Space

1. Medium: 875. Koko Eating Bananas
2. Medium: 1011. Capacity To Ship Packages Within D Days
3. Medium: 1283. Find the Smallest Divisor Given a Threshold

Greedy Techniques

1. Easy: 455. Assign Cookies
2. Easy: 1710. Maximum Units on a Truck