LeetCode Implement Queue Using Stacks

Description

Implement the following operations of a queue using stacks.

• push(x) – Push element x to the back of queue.
• pop() – Removes the element from in front of queue.
• peek() – Get the front element.
• empty() – Return whether the queue is empty.

The original problem is here.

The original code is here.

My Solution

I solve this problem in C++, as below:

/*Implement Queue using Stacks
*Author: shuaijiang
*Email: zhaoshuaijiang8@gmail.com
*/
#include<iostream>
#include<stack>
#include<stdlib.h>
using namespace std;
class Queue {
public:
    stack<int> stack1,stack2;
    // Push element x to the back of queue.
    void push(int x) {
        stack1.push(x);
    }

    // Removes the element from in front of queue.
    void pop(void) {
        if(!stack2.empty())
            stack2.pop();
        else{
            Stack1ToStack2();
            stack2.pop();
        }
    }

    // Get the front element.
    int peek(void) {
        if(!stack2.empty())
            return stack2.top();
        else{
            Stack1ToStack2();
            return stack2.top();
        }
    }

    // Return whether the queue is empty.
    bool empty(void) {
        if(stack1.empty()&&stack2.empty())
            return true;
        else
            return false;
    }
    void Stack1ToStack2(){
        if(!stack2.empty())
            return;
        while(!stack1.empty()){
            int num = stack1.top();
            stack1.pop();
            stack2.push(num);
        }
    }
};

Note

To solve the problem, two stacks are needed.