Data Structures and Algorithms

A comprehensive collection of data structures and algorithms implemented in multiple programming languages. This repository serves as a resource for learning and practicing fundamental computer science concepts.

Overview

This repository contains implementations of various data structures and algorithms, organized by category. Each implementation includes:

• Source code
• Interactive playground (where available)
• Documentation explaining the concept, approach, and complexity

The implementations are primarily in JavaScript, with some examples in other languages like Java, TypeScript, and Go.

Data Structures

Stack

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	Stack using array	Source	JavaScript	-	Easy	Using Array operations	-
2	Stack using linkedlist	Source	JavaScript	-	Easy	Using LinkedList operations	-

Queue

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	Queue using array	Source	JavaScript	Documentation	Easy	Using Array operations	-
2	Queue using linkedlist	Source	JavaScript	Documentation	Easy	Using LinkedList operations	-

SinglyLinkedList

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	SinglyLinkedList implementation	Source	JavaScript	Documentation	Easy	Linked List operations	-

DoublyLinkedList

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	DoublyLinkedList implementation	Source	JavaScript	Documentation	Easy	Linked List operations	-

Tree

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	Binary Search Tree	Source	JavaScript	Documentation	Medium	Tree operations	-

Graphs

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	Unweighted undirected graph	Source	JavaScript	Documentation	Medium	Graph operations	-

HashTable

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	HashTable	Source	JavaScript	-	Medium	Hash operations	-

Algorithms

Array

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	Contains duplicates	Source	Playground	Documentation	Easy	Set/Object	Verify duplicate using set or map/dict/object
2	Two sum2- Input array sorted	Source	Playground	Documentation	Medium	Two pointers	-
3	3 sum	Source	Playground	Documentation	Medium	Two pointers	-
4	Product of array except self	Source	Playground	Documentation	Medium	Prefix and postfix pattern	-
5	Max sum subarray	Source	Playground	Documentation	Medium	Kadane's algorithm	-
6	Minimum size subarray sum	Source	Playground	Documentation	Medium	Sliding window	-
7	Sort Colors	Source	Playground	Documentation	Medium	Two pointers	-
8	Maximum product subarray	Source	Playground	Documentation	Medium	Kadane's algorithm	-
9	Find minimum in rotated sorted array	Source	Playground	Documentation	Medium	Binary search technique	-
10	Maximum Circular subarray	Source	Playground	Documentation	Medium	Kadane's algorithm	-
11	Rotate array	Source	Playground	Documentation	Medium	Two pointers	-
12	Search in rotated sorted array	Source	Playground	Documentation	Medium	Binary search	-
13	Container with most water	Source	Playground	Documentation	Medium	Two pointers	Calculate max area and move shorter pointer inward
14	First missing positive number	Source	JavaScript	Documentation	Hard	In-place hashing	-
15	Best time to buy stock and sell stock	Source	JavaScript	Documentation	Easy	Greedy algorithm	Look for minprice at each position
16	Two missing numbers	Source	JavaScript	Documentation	Medium	Sum and average calculations	-
17	Pascal's Triangle	Source	JavaScript	Documentation	Easy	Array traversal and sequential sum	-
18	Remove Element	Source	JavaScript	Documentation	Easy	Array traversal	-
19	Can place flowers	Source	JavaScript	Documentation	Easy	Array traversal and comparison	-
20	Majority Element	Source	JavaScript	Documentation	Easy	Boyer Moore Voting algorithm	-
21	Pivot Index	Source	JavaScript	Documentation	Easy	Array traversal	-
22	Range Sum queries	Source	JavaScript	Documentation	Easy	Array traversal	-
23	Disappeared numbers	Source	JavaScript	Documentation	Easy	Array traversal	-
24	Identical pairs	Source	JavaScript	Documentation	Easy	Array traversal & map	-
25	Destination City	Source	JavaScript	Documentation	Easy	Array traversal & set	-
26	Set mismatch	Source	JavaScript	Documentation	Easy	Array traversal & marking numbers	-
27	Intersection of arrays	Source	JavaScript	Documentation	Easy	Set and array traversal	-
29	Special array	Source	JavaScript	Documentation	Easy	Frequency counter and array traversal	-
30	Max length between equal chars	Source	JavaScript	Documentation	Easy	Array traversal	-
31	Third largest element	Source	JavaScript	Documentation	Easy	Array traversal	-
32	Odd occurrences	Source	JavaScript	Documentation	Easy	XOR operation	-
33	Max counters	Source	JavaScript	Documentation	Medium	Lazy update strategy	-
34	Tape equilibrium	Source	JavaScript	Documentation	Easy	Prefix sum	-
35	Perm check	Source	JavaScript	Documentation	Easy	Set operations	-
36	Equi leader	Source	JavaScript	Documentation	Medium	Boyer-Moore algorithm	-
37	Count triangles	Source	JavaScript	Documentation	Medium	Two pointers	-
38	Min abs sum of two	Source	JavaScript	Documentation	Medium	Two pointers	-
39	Abs distinct	Source	JavaScript	Documentation	Easy	Two pointers	-
40	Count distinct slices	Source	JavaScript	Documentation	Medium	Sliding window	-

String

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	Longest substring without repeating characters	Source	JavaScript	Documentation	Medium	Sliding Window	set to remove duplicates or map/dict with (char,index) key-value pairs to jump position
2	Longest repeating character replacement	Source	JavaScript	Documentation	Medium	Sliding Window	char frequency dict/map with windowLength-maxFrequency > k check
3	Minimum window substring	Source	JavaScript	Documentation	Hard	Sliding Window	Two char frequecies map/dict for finding minimum length based on having == required
4	Valid anagram	Source	JavaScript	Documentation	Easy	Frequency counting	Balancing char frequency map/dict
5	Group anagrams	Source	JavaScript	Documentation	Medium	Frequency counting	Group anagrams based on unique key(counter or sorted)
6	Valid palindrome	Source	JavaScript	Documentation	Easy	Two pointer	Compare two strings using two pointers
7	Longest palindromic substring	Source	JavaScript	Documentation	Medium	Expanding around center	-
8	Palindromic substrings	Source	JavaScript	Documentation	Medium	Expanding around center	-
9	Encode and decode strings	Source	JavaScript	Documentation	Medium	Basic string and array operations	-
10	Greatest common devisor of strings	Source	JavaScript	Documentation	Easy	Euclidean and String operations	-
11	Reverse words in string	Source	JavaScript	Documentation	Medium	Basic string and array operations	-
12	Length of last word	Source	JavaScript	Documentation	Easy	String traversal	-

Dynamic programming

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	Climbing stairs	Source	JavaScript	Documentation	Medium	Dynamic programming	-
2	Coin change	Source	JavaScript	Documentation	Medium	Dynamic programming	-
3	Longest increasing subsequence	Source	JavaScript	Documentation	Medium	Dynamic programming(Bottom up)	-
4	Longest common subsequence	Source	JavaScript	Documentation	Medium	Two-dimentional bottom up Dynamic programming	-
5	Word break	Source	JavaScript	Source	Medium	Bottom up dynamic programming	-
6	Combination Sum 4	Source	JavaScript	Documentation	Medium	Bottom up Dynamic programming	-
7	House robber	Source	JavaScript	Documentation	Medium	Fibonacci pattern bottom-up dynamic programming	-
8	House robber 2	Source	JavaScript	Documentation	Medium	Bottom-up dynamic programming	-
9	Decode ways	Source	JavaScript	Documentation	Medium	Dynamic programming	-
10	Unique paths	Source	JavaScript	Documentation	Medium	Dynamic programming	-
11	Jump game	Source	JavaScript	Documentation	Medium	Dynamic programming or Greedy	-
12	Min abs sum	Source	JavaScript	Documentation	Medium	Dynamic programming	-
13	Number solitaire	Source	JavaScript	Documentation	Medium	Dynamic programming	-

Binary

No.	Name	Source	Playground	Documentation	Level	Pattern	Hint
1	Sum of two integers	Source	JavaScript	Documentation	Medium	Bitwise operations	-
2	Number of 1 Bits	Source	JavaScript	Documentation	Easy	Brian Kernighans	-
3	Counting Bits	Source	JavaScript	Documentation	Easy	Dynamic programming	-
4	Missing number	Source	JavaScript	Documentation	Easy	Bitwise XOR	-
5	Reverse Bits	Source	JavaScript	Documentation	Easy	Bitwise operations	-

Stack

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	Sort Stack	Source	JavaScript	Documentation	Easy	Stack push & pop	-
2	Balanced Brackets	Source	JavaScript	Documentation	Medium	Stack push and pop	-
3	Reverse Polish Notation	Source	JavaScript	Documentation	Medium	Stack push & pop	-
4	Daily Temperatures	Source	JavaScript	Documentation	Medium	Monotonic decreasing stack	-
5	Number of People See In Queue	Source	JavaScript	Documentation	Medium	Monotonic decreasing stack	-

LinkedList

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	Reverse sublist	Source	JavaScript	Documentation	Easy	List traversal	-
2	Detect cycle in a linkedlist	Source	JavaScript	Documentation	Easy	Floyd's cycle-finding algorithm	-
3	Merge two sorted lists	Source	JavaScript	Documentation	Easy	Arithmetic comparison	-
4	Merge K sorted lists	Source	JavaScript	Documentation	Hard	Divide and conquer	-
5	Remove Kth node from end of list	Source	JavaScript	Documentation	Medium	Two pointers	-
6	Reorder list	Source	JavaScript	Documentation	Medium	Two pointers	-
7	Find middle node	Source	JavaScript	Documentation	Easy	Two pointers	-
8	Find Kth node from end of list	Source	JavaScript	Documentation	Easy	Two pointers	-
9	Partition list	Source	JavaScript	Documentation	Medium	Two pointers	-
10	Remove duplicates	Source	JavaScript	Documentation	Easy	Two pointers	-
11	Binary to decimal	Source	JavaScript	Documentation	Easy	List traversal and math operations	-

DoublyLinkedList

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	Swap first and last	Source	JavaScript	Documentation	Easy	Swap nodes	-
2	Palindrome check	Source	JavaScript	Documentation	Easy	Two pointers	-
3	Swap node pairs	Source	JavaScript	Documentation	Medium	List traversal and pointer updates	-

Tree

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	Maximum depth of binary tree	Source	JavaScript	Documentation	Easy	DFS with recursion	-
2	Same tree	Source	JavaScript	Documentation	Easy	DFS with recursion	-
3	Invert or Flip binary tree	Source	JavaScript	Documentation	Easy	DFS with recursion	-
4	Binary tree maximum path sum	Source	JavaScript	Documentation	Hard	DFS using recursion	-
5	Binary tree level order traversal	Source	JavaScript	Documentation	Easy	BFS traversal	-
6	Serialize and deserialize binary tree	Source	JavaScript	Documentation	Hard	DFS preorder traversal	-
7	Subtree of another tree	Source	JavaScript	Documentation	Easy	DFS with recursion	-
8	Construct binary tree from traversals	Source	JavaScript	Documentation	Medium	DFS with recursion	-
9	Validate BST	Source	JavaScript	Documentation	Medium	DFS using recursion	-
10	Kth smallest element in BST	Source	JavaScript	Documentation	Medium	Inorder traversal	-
11	Lowest Common Ancestor of BST	Source	JavaScript	Documentation	Medium	Tree traversal	-
12	Trie	Source	JavaScript	Documentation	Medium	String character iteration	-
13	Design and Search words Datastructure	Source	JavaScript	Documentation	Medium	Trie and DFS recursion	-
14	Word search 2	Source	JavaScript	Documentation	Hard	Backtracking with Trie	-

Graph

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	Clone graph	Source	JavaScript	Documentation	Medium	DFS using recursion	-
2	Course schedule	Source	JavaScript	Documentation	Medium	DFS using recursion	-
3	Pacific Atlantic waterflow	Source	JavaScript	Documentation	Medium	DFS using recursion	-
4	Number of Islands	Source	JavaScript	Documentation	Medium	DFS using recursion	-
5	Alien dictionary	Source	JavaScript	Documentation	Hard	Topological sorting	-
6	Graph valid tree	Source	JavaScript	Documentation	Medium	Union Find algorithm	-
7	Number of connected components	Source	JavaScript	Documentation	Medium	Union Find algorithm	-
8	Walls and gates	Source	JavaScript	Documentation	Medium	BFS traversal	-
9	Fib frog	Source	JavaScript	Documentation	Medium	Dynamic programming	-

Matrix

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	Set matrix zeros	Source	JavaScript	Documentation	Medium	In-place updates	-
2	Spiral matrix	Source	JavaScript	Documentation	Medium	Boundary traversal	-
3	Rotate image	Source	JavaScript	Documentation	Medium	In-place rotation	-
4	Word search	Source	JavaScript	Documentation	Medium	DFS using recursion	-

Interval

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	Insert interval	Source	JavaScript	Documentation	Medium	Math operations	-
2	Merge interval	Source	JavaScript	Documentation	Medium	Sorting and math operations	-
3	Non-overlapping intervals	Source	JavaScript	Documentation	Medium	Greedy algorithm	-
4	Meeting rooms	Source	JavaScript	Documentation	Medium	Greedy algorithm	-
5	Meeting rooms 2	Source	JavaScript	Documentation	Medium	Two pointers	-
6	Meeting rooms 3	Source	JavaScript	Documentation	Medium	Greedy algorithm	Two minheaps + greedy scheduling + simulation
7	Max non-overlapping segments	Source	JavaScript	Documentation	Medium	Greedy algorithm	-

HashTable

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	Duplicates	Source	JavaScript	Documentation	Easy	Using Map	-
2	Two sum	Source	JavaScript	Documentation	Easy	Using Map	-
3	First non repeating character	Source	JavaScript	Documentation	Easy	Using Map	-
4	Group anagrams	Source	JavaScript	Documentation	Medium	Map methods	-
5	Verify Common Elements	Source	JavaScript	Documentation	Easy	Map methods	-
6	Longest consecutive sequence	Source	JavaScript	Documentation	Medium	Set operations	-
7	Valid Sudoku	Source	JavaScript	Documentation	Medium	Map and Set methods	-
8	Letter combinations	Source	JavaScript	Documentation	Medium	Backtracking with hash mapping	-
9	LRU Cache	Source	JavaScript	Documentation	Medium	Hash Table with linked list	-
10	Maximum number of balloons	Source	JavaScript	Documentation	Easy	Character frequency map	-
11	Isomorphic Strings	Source	JavaScript	Documentation	Easy	Character mapping	-
14	First unique character	Source	JavaScript	Documentation	Easy	Character frequency count	-

Sorting

No.	Name	Source	Live	Documentation	Level	Complexity	Hint
1	Bubble sort	Source	JavaScript	Documentation	Easy	TC: O(n²), SC: O(1)	-
2	Selection sort	Source	JavaScript	Documentation	Easy	TC: O(n²), SC: O(1)	-
3	Insertion sort	Source	JavaScript	Documentation	Easy	TC: O(n²), SC: O(1)	-
4	Merge sort	Source	JavaScript	Documentation	Medium	TC: O(n log n), SC: O(n)	-
5	Quick sort	Source	JavaScript	Documentation	Medium	TC: O(n²), SC: O(log n)	-
6	Heap sort	Source	JavaScript	Documentation	Hard	TC: O(n log n), SC: O(1)	-
7	Radix sort	Source	JavaScript	Documentation	Medium	TC: O(d(n+k)), SC: O(n+k)	-
8	Max product of three	Source	JavaScript	Documentation	Easy	Array sorting	-

Misc

No.	Name	Source	Live	Documentation	Level	Pattern	Hint
1	Frog jump	Source	JavaScript	Documentation	Easy	Mathematical calculation	-
2	Missing element	Source	JavaScript	Documentation	Easy	Mathematical calculation	-
3	Frog river one	Source	JavaScript	Documentation	Easy	Set operations	-
4	Count divisible	Source	JavaScript	Documentation	Easy	Mathematical calculation	-