Algorithms & Data Structures

A reference implementation of core computer science concepts in JavaScript - covering data structures, recursion patterns, algorithm challenges, and built-in method complexity analysis.

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Table of Contents

• Data Structures
  • Singly Linked List
  • Binary Search Tree
  • Graph
• Recursion
• Advanced Algorithms
• Algorithm Challenges
• Utility Reference

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Data Structures

Singly Linked List

03 Data Structures/Singly Linked List/script.js

Custom implementation with a Node class and a SinglyLinkedList class.

Method	Description	Time Complexity
push(val)	Append a node to the tail	O(1)
pop()	Remove and return the tail node	O(n)
shift()	Remove and return the head node	O(1)
unshift(val)	Prepend a node at the head	O(1)
get(index)	Retrieve a node by index	O(n)
printList()	Log all node values to the console	O(n)

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Binary Search Tree

03 Data Structures/Binary Search Tree/script.js

Custom BST implementation with iterative traversal to avoid call-stack overhead.

Method	Description	Time Complexity
insert(value)	Insert a value, ignoring duplicates	O(log n) avg
find(value)	Search for a value; returns the node or undefined	O(log n) avg
BFS()	Breadth-first traversal; returns values level by level	O(n)

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Graph

03 Data Structures/Graph/script.js

Undirected graph using an adjacency list representation.

Method	Description
addVertex(vertex)	Add a new vertex
addEdge(v1, v2)	Create an undirected edge between two vertices
removeEdge(v1, v2)	Remove the edge between two vertices
removeVertex(v)	Remove a vertex and all its associated edges
depthFirstRecursive(start)	DFS traversal from a given starting vertex

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Recursion

04 Recursion/script.js

Function	Description
countDown(n)	Print integers from n down to 0
power(base, exp)	Compute base raised to an exponent
factorial(n)	Compute n!
productOfArray(arr)	Multiply all elements of an array
recursiveRange(n)	Sum all integers from 0 to n
fib(n)	Return the nth Fibonacci number
reverse(str)	Reverse a string

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Advanced Algorithms

05 Advanced/script.js

Dijkstra's Shortest Path

Finds the shortest path between two vertices in a weighted graph using a min-heap priority queue.

Time: O((V + E) log V) — Space: O(V)

Class / Function	Description
WeightedGraph	Undirected weighted graph (adjacency list)
addVertex(v)	Add a vertex
addEdge(v1, v2, weight)	Add a weighted undirected edge
dijkstra(start, end)	Returns { distance, path } for the shortest route
PriorityQueue	Internal min-heap used to always expand the cheapest vertex next

Demo graph (A → E): path A → C → D → F → E, total weight 6

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Algorithm Challenges

01 Questions/

Problem	Description	Approach
FindIntersection	Given two sorted comma-separated number strings, return their common elements	Filter + linear scan - O(n·m)

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Utility Reference

02 Useful-functions/

Array Method Complexity

Method	Returns	Time Complexity
push	New length	O(1)
pop	Removed element	O(1)
unshift	New length	O(n)
shift	Removed element	O(n)
concat / slice / splice	Varies	O(n)
sort	Sorted array	O(n log n)
forEach / map / filter / reduce	Varies	O(n)

Helper Functions (misc.js)

Function	Description
isLetter(c)	Returns true if the character is a letter
isNum(c)	Returns true if the character is a digit (0–9)

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Language

JavaScript (ES6+) - no dependencies, runs in any modern browser or Node.js environment.