用2个stack模拟一个queue

#include <iostream>
#include <stack>
using namespace std;

class MyQueue{
public:
    void push(int value);
    void pop();
    int front();
    int back();
    bool empty();
private:
    stack<int> stackPush;
    stack<int> stackPop;
};

void MyQueue::push(int value)
{
    stackPush.push(value);
}

void MyQueue::pop()
{
    if (stackPop.empty())
        while(!stackPush.empty()){
            stackPop.push(stackPush.top());
            stackPush.pop();
        }

    if (!stackPop.empty())
        stackPop.pop();
    else 
        cout<<"Queue already empty!"<<endl;
}

int MyQueue::front()
{
    if (stackPop.empty())
        while(!stackPush.empty()){
            stackPop.push(stackPush.top());
            stackPush.pop();
        }

    if (!stackPop.empty())
        return stackPop.top();
    else {
        cout<<"Queue already emtpy!"<<endl;
        return -1;
    }
}

int MyQueue::back()
{
    if (!stackPush.empty())
        return stackPush.top();
    
    else if (stackPush.empty() && !stackPop.empty()){
        stack<int> stackTmp;
        while (!stackPop.empty()){
            stackTmp.push(stackPop.top());
            stackPop.pop();
        }
        int returnValue = stackTmp.top();
        while (!stackTmp.empty()){
            stackPop.push(stackTmp.top());
            stackTmp.pop();
        }
        return returnValue;
    }

    else if (stackPush.empty() && stackPop.empty()){
        cout<<"queue already empty!"<<endl;
        return -1;
    }
}

bool MyQueue::empty()
{
    if (stackPush.empty() && stackPop.empty())
        return true;
    return false;
}

int main()
{
    MyQueue myQueue;
    for (int i = 0; i < 10; i++)
    {
        int value = rand()%100;
        cout<<"EnQueuing element : "<<value<<endl;
        myQueue.push(value);
        cout<<"Current Front Element : "<<myQueue.front()<<"      Current Back Element : "<<myQueue.back()<<endl<<endl;
    }
    cout<<"Push over!"<<endl;
    while (!myQueue.empty())
    {
        cout<<"DeQueuing element : "<<myQueue.front()<<endl;
        myQueue.pop();
    }

    return 0;
}

EOF