algorithms

Arrays store elements in contiguous memory. Access is O(1). Search and modification require iterating. This guide covers six algorithms that appear repeatedly in array problems: binary search, two pointers, sliding window, prefix sums, divide and conquer, and the Dutch national flag.

Recursion and iteration are interchangeable. Any loop can be rewritten as recursion, and any recursion can be rewritten as a loop using an explicit stack. The difference is cost. Recursion consumes the call stack and adds per-call overhead. Iteration does neither. The right choice depends on the problem structure and the language.