Stack Queue — DSA Interview Problems

Stack Queue is LIFO and FIFO structures behind parsing, monotonic, and BFS patterns, and it shows up regularly in technical interviews. Stack/queue questions test matching/parsing, monotonic-stack tricks, and level-order processing.

Our library indexes 17 Stack Queue problems (4 easy, 9 medium, 4 hard), each solved brute-force → optimal in Java and Python with a line-by-line walkthrough and interview talking points. They're grouped below by the curriculum module that teaches the underlying pattern, so related problems reinforce one another.

If you remember one thing about Stack Queue, make it this: A monotonic stack answers 'next greater/smaller element' style questions in a single O(n) pass. Once that clicks, the signature patterns — monotonic stack, parsing with a stack, BFS queue — start to feel like a checklist you run on every new problem.