Stacks and queues

Stacks and queues both store sequences of items, but they remove them in different orders.

Stack: LIFO

Last in, first out. The most recently pushed item is the first one popped. A stack is useful for undo operations and depth-first search.

C# | Stack

var stack = new Stack<int>();
stack.Push(10);
stack.Push(20);
int value = stack.Pop(); // 20

Queue: FIFO

First in, first out. The oldest enqueued item is the first dequeued. Queues are useful for work scheduling and breadth-first search.

C# | Queue

var queue = new Queue<int>();
queue.Enqueue(10);
queue.Enqueue(20);
int value = queue.Dequeue(); // 10

Comparing operations

Operation	Stack	Queue
Add	Push	Enqueue
Remove	Pop	Dequeue
Typical time complexity	O(1)	O(1)

Typical complexities assume an appropriate implementation and exclude occasional resizing costs.