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
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
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
1	SinglyLinkedList implementation	Source	JavaScript	Documentation	Easy	Linked List operations

DoublyLinkedList

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

Tree

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

Graphs

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

HashTable

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

Algorithms

Array

No.	Name	Source	Live	Documentation	Level	Pattern
1	Contains duplicates	Source	Playground	Documentation	Easy	Set/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
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
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

String

No.	Name	Source	Live	Documentation	Level	Pattern
1	Longest substring without repeating characters	Source	JavaScript	Documentation	Medium	Sliding Window
2	Longest repeating character replacement	Source	JavaScript	Documentation	Medium	Sliding Window
3	Minimum window substring	Source	JavaScript	Documentation	Hard	Sliding Window
4	Valid anagram	Source	JavaScript	Documentation	Easy	Frequency counting
5	Group anagrams	Source	JavaScript	Documentation	Medium	Frequency counting
6	Valid palindrome	Source	JavaScript	Documentation	Easy	Two pointer
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
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

Binary

No.	Name	Source	Playground	Documentation	Level	Pattern
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
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
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
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
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
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

Matrix

No.	Name	Source	Live	Documentation	Level	Pattern
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
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

HashTable

No.	Name	Source	Live	Documentation	Level	Pattern
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
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)