Core Coding Questions (Beginners Must-Do)
Fibonacci Series (Iterative and Recursive)
Factorial (Iterative & Recursive)
Sum of N Numbers
Sum of Digits
Count Digits
Reverse a Number
Swap Numbers (Without Temp Variable)
Check Prime Number
Print All Prime Numbers in Range
Leap Year Check
Find Maximum of 3 Numbers
Palindrome Number
Armstrong Number
Armstrong Number in Range
Strong Number
Perfect Number
Automorphic Number
Duck Number
Buzz Number
Krishnamurthy Number
Spy Number
Neon Number
Happy Number
Evil Number
Twin Prime Numbers
Palindromic Prime
Magic Number
Harshad Number
Disarium Number
Number System & Mathematical Programs
GCD (Iterative & Recursive)
LCM
Power of a Number
Count Trailing Zeros in Factorial
Sum of Series 1+1/2+1/3+...
Sum of Series 1²+2²+…+n²
Sum of Cube of Digits
Convert Binary to Decimal
Convert Decimal to Binary
Convert Decimal to Octal
Convert Octal to Decimal
Convert Decimal to Hex
Convert Hex to Decimal
Number to Words
ASCII of Character
Roots of Quadratic Equation
Arrays & Searching/Sorting
Linear Search
Binary Search
Bubble Sort
Insertion Sort
Selection Sort
Quick Sort
Merge Sort
Reverse an Array
Find Second Largest Number in Array
Frequency of Elements in Array
Find Missing Number in Array
Merge Two Sorted Arrays
Move Zeros to End
Dutch National Flag Problem (Sort 0s, 1s, 2s)
Kadane’s Algorithm (Max Subarray Sum)
Stock Buy and Sell (Best Time)
Rotate Array by K Positions
Leaders in Array
Two Sum Problem
Triplet Sum Equals Zero
Find Duplicates in Array
Remove Duplicates from Sorted Array
Longest Increasing Subsequence
Strings & Text Processing
Reverse a String
String Palindrome
Count Vowels & Consonants
Count Digits in String
String Length (Manual)
Remove Spaces
Remove Vowels
Remove Consonants
Toggle Case
Convert String to Uppercase/Lowercase
Title Case Conversion
Count Words in a Sentence
First Repeating Character
First Non-Repeating Character
Check Anagram
Count Character Frequency
Find Substring
Replace Characters
Remove Duplicates
Sort Characters
Longest Word in Sentence
Shortest Word
Reverse Words in Sentence
Count Special Characters
Remove Punctuation
Compress String (RLE)
String to Integer (without library)
Integer to String
Valid Parentheses
Minimum Insertions for Palindrome
Count Occurrences of Word
Find Most Frequent Word
String Rotation
Find All Substrings
Count Palindromic Substrings
Longest Palindromic Substring
Longest Common Prefix
Group Anagrams
Edit Distance
Z-Algorithm for Pattern Matching
KMP Algorithm
Rabin-Karp Algorithm
Boyer-Moore Algorithm
Reverse Only Alphabets
Mask Phone Number
Valid Email Pattern Check
Check Pangram
Find Missing Character
Linked List & Trees
Reverse Linked List
Detect Loop in Linked List
Merge Two Sorted Linked Lists
Middle of Linked List
Nth Node from End in Linked List
Binary Tree Inorder Traversal (Recursive & Iterative)
Lowest Common Ancestor in BST
Level Order Traversal
Binary Search Tree – Insert & Search
Height of Binary Tree
Check if BST is Valid
Count Nodes in Binary Tree
Invert a Binary Tree
Graph & Advanced DSA
BFS (Breadth-First Search)
DFS (Depth-First Search)
Graph Cycle Detection (DFS/BFS)
Dijkstra's Algorithm
Bellman-Ford Algorithm
Topological Sort
Kahn’s Algorithm
Kruskal’s MST
Prim’s Algorithm
Disjoint Set Union (DSU)
Union Find with Path Compression
Floyd Warshall
Count Connected Components
Check Bipartite Graph
Flood Fill Algorithm
Number of Islands
Recursion & Backtracking
Factorial using Recursion
Fibonacci using Recursion
Sum of N Numbers using Recursion
GCD using Recursion
Check Palindrome using Recursion
Reverse String using Recursion
Print Array in Reverse
Count Digits Recursively
Tower of Hanoi
Print all Subsets
Generate All Permutations
Recursive Binary Search
Nth Fibonacci Term
Subset Sum Problem
N-Queens Problem
Rat in a Maze
Sudoku Solver
Pattern Printing (Beginner Practice)
Solid Rectangle
Hollow Rectangle
Left Aligned Triangle
Right Aligned Triangle
Star Pyramid
Inverted Number Pyramid
Half Pyramid Using Numbers
Pascal’s Triangle
Floyd’s Triangle
Diamond Pattern
Hollow Diamond
Butterfly Pattern
Zig-Zag Pattern
Palindromic Pyramid
Binary Triangle
File Handling & Real-World Programs
File Read/Write Program
Count Lines, Words, and Characters in File
Merge Contents of Two Files
Append Text to Existing File
Replace a Word in File
Sort Data from File
Find Word Frequency in File
Encrypt/Decrypt Text (Caesar Cipher)
Count Occurrences of a Word in a File
Simple Calculator using Switch
ATM Simulation Program
Railway Ticket Booking Logic
Billing System Program
User Login & Password Masking
URL Validator
Email Validator using Regex
Extract Phone Numbers from Text
Input Validation Program
Aptitude & Competitive Programming Favorites
Find Element Occurring Odd Number of Times
Find Single Number (XOR Trick)
Check for Power of Two
Count Set Bits
Largest Power of 2 Less Than N
XOR of All Elements
Detect Duplicate in O(1) space
Rearrange Array Alternating + and -
Convert Infix to Postfix
Evaluate Postfix Expression
Check Balanced Parentheses
Largest Histogram Area
Maximum Area in Binary Matrix
Next Greater Element
Trapping Rainwater
Minimum Platforms Required (Train Problem)
Merge Intervals
Activity Selection
Job Scheduling Problem
Josephus Problem
Leaders in Array
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