# <queue>

**[<queue>](https://en.cppreference.com/w/cpp/header/queue)** provides `std::queue<T>` (FIFO) and `std::priority_queue<T>` (min/max heap). They are container adapters—wrappers around a deque or vector that expose only the queue semantics.

Use `queue` for FIFO (front end, back end), and `priority_queue` for keeping elements sorted by a comparator.

## Example

This example demonstrates FIFO queuing and priority queue behavior where the largest element is always at the top.

```cpp
// compile: g++ -std=c++11 -o queueexample queueexample.cpp
// run: ./queueexample
// description: FIFO queue and priority queue

#include <queue>
#include <iostream>

int main() {
    std::queue<int> fifo;
    fifo.push(1);
    fifo.push(2);
    fifo.push(3);
    
    std::cout << "fifo front: " << fifo.front() << "\n";
    fifo.pop();
    std::cout << "after pop, front: " << fifo.front() << "\n";
    
    std::priority_queue<int> pq;
    pq.push(3);
    pq.push(1);
    pq.push(2);
    
    std::cout << "priority_queue top: " << pq.top() << "\n";
    
    return 0;
}
```