Why does stack default to deque?

deque supports efficient operations at both ends; you can specialize stack with vector if that fits better.

BFS with queue, DFS with stack?

That matches typical iterative patterns; recursive DFS uses the call stack implicitly.

What kind of heap is priority_queue?

Default is a max-heap; use greater or a custom comparator for a min-heap.

Why not vector under queue?

queue needs efficient front pop; deque is the usual default for that interface.

C++ stack, queue & priority_queue: Container Adapters & BFS/DFS

2026년 3월 12일 · 10분 읽기 · 수정 2026년 3월 12일 Beginner tutorial

이 글의 핵심

Compare stack, queue, and priority_queue with examples for graph traversal and scheduling.

For stacks and queues as abstract types and how they show up in BFS/DFS, see stacks and queues.

Comparison

Feature	stack	queue	priority_queue
Order	LIFO	FIFO	Priority (heap)
Access	top()	front(), back()	top()
Push	push()	push()	push()
Pop	pop()	pop()	pop()

stack

push, top, pop, size, empty — no random access.

queue

push, front, back, pop.

priority_queue

Default max-heap; priority_queue<T, vector<T>, greater<T>> for min-heap.

Examples

DFS with explicit stack (iterative).
BFS with queue storing {node, distance} for shortest path in unweighted graphs.
Task scheduling with priority_queue and custom operator< or comparator struct.

Common pitfalls

No operator[] on stack/queue — drain or use deque/vector if index access is required.
pop() returns void — read top()/front() first.
Custom types in priority_queue need operator< or explicit comparator type.

FAQ

When to use each adapter; deque for double-ended work; min-heap with greater; dynamic sizing vs fixed arrays; O(1) vs O(log n) for priority_queue; thread safety requires external locking.

C++ container adapters
C++ data structures from scratch
C++ stack overflow (concept)

Keywords

std::stack, std::queue, priority_queue, BFS, DFS, LIFO, FIFO, heap, STL