#include <iostream>
#include <queue>

int main() {
    std::queue<int> myQueue;

    // 入队
    myQueue.push(10);
    myQueue.push(20);
    myQueue.push(30);

    std::cout << "队列大小: " << myQueue.size() << std::endl;

    // 访问队头和队尾
    std::cout << "队头元素: " << myQueue.front() << std::endl;
    std::cout << "队尾元素: " << myQueue.back() << std::endl;

    // 出队
    myQueue.pop();
    std::cout << "出队后队头元素: " << myQueue.front() << std::endl;

    // 遍历队列
    std::cout << "队列中的元素: ";
    while (!myQueue.empty()) {
        std::cout << myQueue.front() << " ";
        myQueue.pop();
    }
    std::cout << std::endl;

    return 0;
}