🎯 Practice Problems
Curated collection of algorithm problems organized by difficulty and category. Click to learn the underlying concepts.
Two Sum
Find two numbers that add up to target
Valid Parentheses
Check if brackets are properly matched
Merge Sorted Arrays
Merge two sorted arrays in-place
Maximum Subarray
Find contiguous subarray with largest sum
Binary Search
Search for target in sorted array
First Bad Version
Find first bad commit using binary search
Climbing Stairs
Count ways to climb n stairs (1 or 2 steps)
Remove Duplicates
Remove duplicates from sorted array in-place
3Sum
Find all triplets that sum to zero
Container With Most Water
Find max water between two lines
Longest Substring Without Repeating
Longest substring without repeating chars
Longest Palindromic Substring
Find longest palindrome substring
Search in Rotated Array
Search in rotated sorted array
Combination Sum
Find combinations summing to target
Permutations
Generate all permutations of array
Coin Change
Minimum coins to make amount
Longest Common Subsequence
LCS of two strings
Kth Largest Element
Find kth largest element in array
Course Schedule
Detect cycle in directed graph (prerequisite check)
Implement Trie
Implement trie insert and search
Word Break
Can string be segmented into dictionary words
Number of Islands
Count connected islands in grid
Minimum Window Substring
Smallest substring containing all target chars
N-Queens
Place N queens on NxN board
Merge K Sorted Lists
Merge k sorted linked lists
Sudoku Solver
Solve 9x9 Sudoku puzzle
Longest Increasing Subsequence
Find LIS length
Maximum XOR of Two Numbers
Find max XOR using binary trie
Activity Selection
Max non-overlapping activities
Edit Distance
Minimum operations to convert string