// 03
Problem Walkthroughs
Seven problems worked through with ROPITA, each with implementation, test cases, and complexity analysis.
Two Sum
Find two numbers in an array that add to a target
Hash Map / Setintroductory
Valid Parentheses
Check if a string of brackets is properly balanced
Stackintroductory
Valid Palindrome
Check if a string is a palindrome (ignoring non-alphanumeric characters)
Two Pointersintroductory
Binary Search
Search for a target value in a sorted array efficiently
Binary Searchintroductory
Best Time to Buy and Sell Stock
Find the maximum profit from buying and selling a stock once
Sliding Windowintermediate
Three Sum
Find all unique triplets in an array that sum to zero
Two Pointersintermediate
Number of Islands
Count distinct islands in a grid using depth-first search
Depth-First Searchintermediate