What is the difference between a stack and a queue, and when would you use one over the other?

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Krishnapriya Rajeev · Answer

A stack and a queue are two different data structures that are used to store and manage a collection of elements.

A stack is a last-in, first-out (LIFO) data structure, which means that the last element added to the stack is the first one to be removed. A stack typically supports two main operations: push, which adds an element to the top of the stack, and pop, which removes the element from the top of the stack.

They are used:

when the order in which elements are added or removed is important. For example, if you need to process a list of nested functions or expressions, a stack can be used to keep track of the order in which they should be evaluated.
for backtracking algorithms, where you need to undo a series of operations in reverse order.

A queue is a first-in, first-out (FIFO) data structure, which means that the first element added to the queue is the first one to be removed. A queue typically supports two main operations: enqueue, which adds an element to the end of the queue, and dequeue, which removes the element from the front of the queue.

They are used:

when you need to process elements in the order in which they were added. For example, if you are implementing a print queue, where print jobs are added to the queue in the order they are received and processed in the same order.
in breadth-first search algorithms, where you need to visit all the nodes in a graph level by level.

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What is the difference between a stack and a queue, and when would you use one over the other?

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