What is the stack pattern and when should you use it in coding interviews?

The stack pattern uses a last-in-first-out data structure to process elements in reverse order, match pairs, or track state that needs to be unwound. Use it when the problem involves matching opening and closing symbols like parentheses, processing elements in reverse of their arrival order, evaluating expressions, maintaining a history that can be undone, or finding the next greater or smaller element. The stack naturally handles nested structures because the most recently opened scope is the first one closed. Most stack problems run in O of n time and O of n space.