Algorithms and Data Structures

A collection of classical data structures and algorithms implemented in Typescript. Click the 📹 emoji for tutorials.

Data structure series: View the entire series in order here.

Algorithms/leetcode series: View the entire series in order here

The repository's primary goal is educational. Hence, all implementations include a prolific number of comments which guide the reader.

You can use this package in your projects if you so wish. Test coverage will be kept at 100%. To install the package, use npm or yarn:

npm install dsa-ts --save

yarn add dsa-ts

Data Structures

• Sequences
  • 📹 Linked List
  • 📹 Stack
  • 📹 Queue
  • Double-ended Queue
  • 📹 Circular Buffer
• Priority Queues
  • 📹 Binary Heap
  • D-Heap
  • 📹 Indexed Binary Heap
  • Mergeable Heaps
    • 📹 Binomial Heap
    • 📹 Lazy Binomial Heap
    • 📹 Fibonnaci Heap
• Search Trees
  • 📹 Binary Search Tree
  • 📹 AVL Tree
  • Red-black Tree
  • B-Tree
• Hash Tables
  • 📹 Hash Table (Separate Chaining)
  • Hash Table (Open Addressing)
    • Hash Table (Linear Probing)
    • Hash Table (Quadratic Probing)
    • Hash Table (Double Hashing)

Algorithms

Following algoritms/problems compiled from Grokking, EPI, and AlgoExpert

Array

• 509. Fibonacci Number (Easy)
• 896. Monotonic Array (Easy)
• 238. Product of Array Except Self (Medium)
• 48. Rotate Image (Medium)
• 33. Search in Rotated Sorted Array (Medium)
• 34. Find First and Last Position of Element in Sorted Array (Medium)
• 189. Rotate Array (Easy)
• 118. Pascal's Triangle (Easy)
• 54. Spiral Matrix (Medium)
• 280. Wiggle Sort (Medium)
• 36. Valid Sodoku (Medium)
• 48. Rotate Image (Medium)
• 4. Median of Two Sorted Arrays (Hard)
• 84. Largest Rectangle in Histogram (Hard)
• 1200. Minimum Absolute Difference (Easy)

Sliding Window

• 209. Minim Size Subarray Sum (Medium)
• 904. Fruit Into Baskets (Medium)
• 3. Longest Substring Without Repeating Characters (Medium)
• 1004. Max Consecutive Ones III (Medium)
• 567. Permutation in String (Medium)
• 438. Find All Anagrams in a String (Medium)
• 46. Minimum Window Substring (Hard)
• 76. Minimum Window Substring (Hard)
• 239. Sliding Window Maximum (Hard)

Two Pointers

• 167. Two Sum II (Easy)
• 283. Move Zeroes
• 26. Remove Duplicates from Sorted Array (Easy)
• 977. Squares of a Sorted Array (Easy)
• 15. 3Sum (Medium)
• 16. 3Sum Closest (Medium)
• 713. Subarray Product Less than K (Medium)
• 75. Sort Colors (Medium)
• 18. 4Sum (Medium)
• 845. Longest Mountain in Array (Medium)
• 844. Backspace String Compare (Easy)
• 581. Shortest Unsorted Continuous Subarray (Easy)

Fast and Slow Pointers

• 141. Linked List Cycle (Easy)
• 142. Linked List Cycle II (Easy)
• 876. Middle of the Linked List (Easy)
• 234. Palindrome Linked List (Easy)
• 143. Reorder List (Medium)
• 457. Circular Array Loop (Medium)

Binary Search

• 74. Search a 2D Matrix (Medium)
• 240. Search a 2D Matrix II (Medium)
• 📹 454. 4Sum II (Medium)
• 📹 875. Koko Eating Bananas (Medium)

Merge Intervals

• 📹 56. Merge Intervals (Medium)
• 57. Insert Interval (Hard)
• 252 Meeting Rooms (Easy)
• 253. Meeting Rooms (Medium)
• 452. Minimum Number of Arrows to Burst Balloons (Medium)
• 986. Interval List Intersection (Medium)

Cyclic Sort

• 268. Missing Number (Easy)
• 448. Find All Numbers Disappeared in an Array (Easy)
• 287. Find the Duplicate Number (Medium)
• 442. Find All Duplicates in an Array (Medium)
• 41. First Missing Positive (Hard)

String

• 20. Valid Parentheses (Easy)
• 680. Valid Palindrome II (Easy)
• 557. Reverse Words in a String III (Easy)
• 929. Unique Email Addresses (Easy)
• 459. Repeated Substring Pattern (Easy)
• 415. Add Strings (Easy)
• 14. Longest Common Prefix (Easy)
• 583. Delete Operation for Two Strings (Medium)
• 767. Reorganize String (Medium)
• 856. Score of Parentheses (Medium)
• 1249. Minimum Remove to Make Valid Parentheses (Medium)
• 1268. Search Suggestions System (Medium)
• 791. Custom Sort String (Medium)
• 890. Find and Replace Pattern (Medium)
• 678. Valid Parenthesis String (Medium)
• 227. Basic Calculator II (Medium)
• 49. Group Anagrams (Medium)
• 214. Shortest Palindrome (Hard)
• 632. Smallest Range Covering Elements from K Lists (Hard)

Linked List

• 21. Merge Two Sorted Lists (Easy)
• 160. Intersection of Two Linked Lists (Easy)
• 83. Remove Duplicates from Sorted List (Easy)
• 19. Remove Nth Node From End of List (Medium)
• 138. Copy List with Random Pointer (Medium)
• 19. Remove Nth Node from End of List (Medium)
• 2. Add Two Numbers (Medium)
• 138. Copy List with Random Pointer (Medium)
• 234. Palindrome Linked List (Easy)
• 86. Partition List (Medium)

Linked List Reversal

• 206. Reverse Linked List (Easy)
• 92. Reverse Linked List II (Medium)
• 61. Rotate List (Medium)
• 24. Swap Nodes in Pairs (Medium)
• 328. Odd Even Linked List (Medium)
• 25. Reverse Nodes in k-Group (Hard)

Tree

• 617. Merge Two Binary Trees (Easy)
• 226. Invert Binary Tree (Easy)
• 110. Balanced Binary Tree (Easy)
• 101. Symmetric Tree (Easy)
• 94. Binary Tree Inorder Traversal (Medium)
• 144. Binary Tree Preorder Traversal (Medium)
• 145. Binary Tree Postorder Traversal (Hard)
• 236. Lowest Common Ancestor of a Binary Tree (Medium)
• 297. Serialize and Deserialize Binary Tree (Hard)
• 145. Binary Tree Postorder Traversal Tree (Hard)

Tree Breadth First Search

• 101. Symmetric Tree (Easy)
• 102. Binary Tree Level Order Traversal (Medium)
• 107. Binary Tree Level Order Traversal II (Easy)
• 103. Binary Tree Zigzag Level Order Traversal (Medium)
• 637. Average of Levels in Binary Tree (Easy)
• 111. Minimum Depth of Binary Tree (Easy)
• 104. Maximum Depth of Binary Tree (Easy)
• 116. Populating Next Right Pointers in Each Node (Medium)
• 199. Binary Tree Right Side View (Medium)

Tree Depth First Search

• 112. Path Sum (Easy)
• 100. Same Tree (Easy)
• 113. Path Sum II (Medium)
• 105. Construct Binary Tree from Preorder and Inorder Traversal (Medium)
• 114. Flatten Binary Tree to Linked List (Medium)
• 129. Sum Root to Leaf Numbers (Medium)
• 437. Path Sum III (Easy)
• 543. Diameter of a Binary Tree (Easy)
• 124. Binary Tree Maximum Path Sum (Hard)
• 98. Validate Binary Search Tree (Medium)
• 1028. Recover a Tree From Preorder Traversal (Hard)

Stack/Queues/Monotonic Queues

• 150. Evaluate Reverse Polish Notation (Medium)
• 496. Next Greater Element I (Easy)
• 503. Next Greater Element II (Medium)
• 901. Online Stock Span (Medium)
• 581. Shortest Unsorted Continuous Subarray (Easy)
• 42. Trapping Rain Water (Hard)
• 907. Sum of Subarray Minimums (Medium)
• 891. Sum of Subsequence Widths (Hard)
• 828. Count Unique Characters of All Substrings of a Given String (Hard)
• 316. Remove Duplicate Letters (Hard)
• 402. Remove K Digits (Medium)
• 768. Max Chunks To Make Sorted II (Hard)
• 321. Create Maximum Number (Hard)
• 856. Score of Parentheses (Medium)
• 334. Increasing Triplet Subsequence (Medium)

Two Heaps

• 295. Find Median from Data Stream (Hard)
• 480. Sliding Window Median (Hard)
• 502. IPO (Hard)

Top K Elements

• 215. Kth Largest Element in an Array (Medium)
• 973. K Closest Points to Origin (Meidum)
• 1000. Minimum Cost to Merge Stones (Hard)
• 347. Top K Frequent Elements (Medium)
• 451. Sort Characters by Frequency (Medium)
• 703. Kth Largest Element in a Stream (Easy)
• 658. Find K Closest Elements (Medium)
• 767. Reorganize String (Medium)
• 358. Rearrange String k Distance Apart (Hard)
• 895. Maximum Frequency Stack (Hard)

K-way Merge

• 23. Merge K Sorted Lists (Hard)
• 378. Kth Smallest Element in a Sorted Matrix (Medium)
• 373. Find K Pairs with Smallest Sums (Medium)

Design

• 146. LRU Cache (Medium)
• 155. Min Stack (Easy)
• 622. Design Circular Queue (Medium)
• 232. Implement Queue using Stacks (Easy)

Backtracking

• 78. Subsets (Easy)
• 90. Subsets II (Medium)
• 46. Permutations (Medium)
• 47. Permutations II (Medium)
• 60. Permutation Sequence (Medium)
• 20. Valid Parentheses (Easy)
• 22. Generate Parentheses (Hard)
• 39. Combination Sum (Medium)
• 40. Combinatin Sum II (Medium)
• 216. Combination Sum III (Medium)
• 77. Combinations (Medium)
• 526. Beautiful Arrangement (Medium)
• 784. Letter Case Permutation (Easy)
• 224. Basic Calculator (Hard)
• 96. Unique Binary Search Trees (Medium)
• 980. Unique Paths III (Hard)
• 131. Palindrome Partitioning (Medium)
• 17. Letter Combinations of a Phone Number (Medium)
• 51. N-Queens (Hard)
• 52. N-Queens II (Hard)
• 37. Sudoker Solver (Hard)
• 93. Restore IP Addresses (Medium)
• 79. Word Search (Medium)
• 212. Word Search II (Hard)
• 140. Word Break II (Hard)
• 10. Regular Expression Matching (Hard)
• 126. World Ladder II (Hard)

Greedy

• 763. Partition Labels (Medium)
• 407. Queue Reconstruction by Height (Medium)
• 1046. Last Stone Weight (Easy)
• 1029. Two City Scheduling (Easy)
• 714. Best Time to Buy and Sell Stock with Transaction Fee (Medium)
• 765. Couples Holding Hands (Hard)
• 452. Minimium Number of Arrows to Burst Balloons (Medium)
• 392. Is Subsequence (Easy)
• 621. Task Scheduler (Medium)
• 767. Reorganize String (Medium)
• 435. Non-overlapping Intervals (Medium)
• 134. Gas Station (Medium)
• 314. Remove Duplicate Letters (Medium)
• 55. Jump Game (Medium)
• 45. Jump Game II (Hard)
• 630. Course Schedule III (Hard)
• 135. Candy (Hard)
• 402. Remove K Digits (Medium)

Dynamic Programming

• 5. Longest Palindromic Substring (Medium)
• 300. Longest Increasing Subsequence (Medium)
• 1048. Longest String Chain (Medium)
• 72. Edit Distance (Hard)
• 97. Interleaving String (Hard)
• 188. Best Time to Buy and Sell Stock IV (Hard)
• 787. Cheapest Flights Within K Stops (Medium)

Graph BFS/DFS

• 127. Word Ladder (Medium)
• 301. Remove Invalid Parentheses (Hard)

Topological Sort

• 207. Course Schedule (Medium)
• 210. Course Schedule II (Medium)
• 269. Alien Dictionary (Hard)
• 444. Sequence Reconstruction (Hard)
• 310. Minimum Height Trees (Medium)

Union Find

• 128. Longest Consecutive Sequence (Hard)
• 200. Number of Islands (Medium)
• Graph Valid Tree
• Number of Connected Components in an Undirected Graph

Tries

• 208. Implement Trie (Prefix Tree) (Medium)
• 676. Implement Magic Dictionary (Medium)
• 677. Map Sum Pairs (Medium)
• 648. Replace Words (Medium)
• 421. Maximum XOR of Two Numbers in an Array (Medium)
• 692. Top K Frequent Words (Medium)
• 1032. Stream of Characters (Hard)
• 211. Add and Search Word - Data structure design (Medium)
• 212. Word Search II (Hard)
• 472. Concatenated Words (Hard)
• 336. Palindrome Pairs (Hard)
• Index Pairs of a String
• Design Search Autocomplete System
• Word Squares

Bit Manipulation

• 231. Power of Two (Easy)
• 201. Bitwise AND of Numbers Range (Easy)
• 461. Hamming Distance (Easy)
• 338. Counting Bits (Medium)
• 136. Single Number (Easy)
• 137. Single Number II (Medium)
• 260. Single Number III (Medium)
• 1109. Complement of Base 10 Integer (Easy)
• 832. Flipping an Image (Easy)
• 476. Number Complement (Easy)
• 784. Letter Case Permutation (Easy)
• 169. Majority Element (Easy)
• 318. Maximum Product of Word Lengths (Medium)
• 477. Total Hamming Distance (Medium)

Other

• 731. My Calendar II (Medium)
• 731. My Calendar III (Hard)
• 315. Count of Smaller Numbers After Self (Hard)

Minimum Spanning Trees

Shortest Paths

All-Pairs Shortest Paths

Maximum Flows and Minimum Cuts

References

• Fundamental Data Structures
• Introduction to Algorithms by Thomas H. Cormen, Charles E. Leiserson, Ronald L. Rivest, and Clifford Stein
• Algorithm Design by Jon Kleinberg and Éva Tardos
• Algorithms by William Fiset
• Algorithms by Jeff Erickson
• Stanford CS 166
• Harvard CS 224

License

This repository is released under the MIT license. In short, this means you are free to use this software in any personal, open-source or commercial projects