Implement a stack by a single queue

stack_by_queue.cpp

#include <queue>

class Stack {
    queue<int> _q;
public:
    // Push element x onto stack.
    void push(int x) {
        _q.push(x);
    }

    // Removes the element on top of the stack.
    void pop() {
        for(int i = 0; i < _q.size() - 1; i++){
            int temp = _q.front();
            _q.pop();
            _q.push(temp);
        }
        _q.pop();
    }

    // Get the top element.
    int top() {
        for(int i = 0; i < _q.size() -1; i++){
            int temp = _q.front();
            _q.pop();
            _q.push(temp);
        }
        int top = _q.front();
        _q.pop();
        _q.push(top);
        return top;
    }

    // Return whether the stack is empty.
    bool empty() {
        return _q.empty();    
    }
};