Stack vs Queue
Two of the most fundamental linear data structures, differing only in the order they release elements — LIFO vs FIFO — which shapes what each is used for.
A linear data structure that follows the Last-In, First-Out (LIFO) principle. Elements are added (pushed) and removed (popped) from the same end, called the 'top'.
When to use it
Use a Stack for LIFO (Last-In, First-Out) needs: undo/redo history, expression/parenthesis matching, function call stacks, and depth-first traversal.
A linear data structure that follows the First-In, First-Out (FIFO) principle. Elements are added (enqueued) at the rear and removed (dequeued) from the front, like a line of people.
When to use it
Use a Queue for FIFO (First-In, First-Out) needs: task/job scheduling, breadth-first traversal, print/request queues, and buffering data between producers and consumers.
Key Differences
- Stack: Last-In, First-Out (LIFO). Queue: First-In, First-Out (FIFO).
- Stack adds/removes from the same end (the "top"); Queue adds at the rear and removes from the front.
- Both support O(1) push/pop or enqueue/dequeue with an array-backed or linked implementation.
- Stacks power recursion and DFS; Queues power BFS and scheduling.
Pick the structure that matches your access pattern: reversal / most-recent-first → Stack, in-order / fairness → Queue.