【LeetCode 232_数据结构_队列_实现】Implement Queue using Stacks

class Queue {
public:
    // Push element x to the back of queue.
    void push(int x) {
        while (!nums.empty()) {
            nums_assist.push(nums.top());
            nums.pop();
        }
        nums.push(x);
        while (!nums_assist.empty()) {
            nums.push(nums_assist.top());
            nums_assist.pop();
        }
    }

    // Removes the element from in front of queue.
    void pop(void) {
        nums.pop();
    }

    // Get the front element.
    int peek(void) {
        return nums.top();
    }

    // Return whether the queue is empty.
    bool empty(void) {
        return nums.empty();
    }
private:
    stack<int> nums, nums_assist;
};