Hash Maps: The O(1) Superpower

How a hash map jumps straight to a value, and how it turns the famous Two Sum problem from O(n²) into one O(n) pass. How hashing works When two keys land in the same bucket it’s a collision; the bucket then holds a tiny list. Good hash functions spread keys evenly, so buckets stay short and lookups stay O(1) on average. Two Sum: the most famous interview question Given nums…