每日一题——栈实现队列，队列实现栈

1，用两个栈实现队列
2，用两个队列实现栈

栈->队列思路：入队时，直接往stack1压入元素；     出队时，判断stack2是否有元素，有则直接弹出栈顶元素，没有则将stack1中的元素一一压入stack2，再弹出stack2的栈顶元素。class MyQueue {public:    stack<int> stack1;    stack<int> stack2;    MyQueue() {        // do intialization if necessary    }    void push(int element) {        // write your code here        stack1.push(element);    }    int pop() {        // write your code here        if(stack2.empty())        {            while(!stack1.empty())            {                stack2.push(stack1.top());                stack1.pop();            }            int ret = stack2.top();            stack2.pop();            return ret;        }        else        {            int ret = stack2.top();            stack2.pop();            return ret;        }    }    int top() {        // write your code here        if(stack2.empty())        {            while(!stack1.empty())            {                stack2.push(stack1.top());                stack1.pop();            }            return stack2.top();        }        else            return stack2.top();    }};

队列->栈思路：有两个队列，一个用来进出栈的，另一个是中转站。入栈时，直接往queue1放进元素；出栈时，先将queue1中前count-1个元素依次放进queue2，然后将最后一个元素出队列。class MyStack {public:    queue<int> queue1;    queue<int> queue2;    MyStack() {        // do intialization if necessary    }    void push(int element) {        // write your code here         queue *pushtmp;        if(!IsQueueEmpty(queue1))        {            pushtmp = queue1;        }        else        {            pushtmp = queue2;        }        EnQueue(pushtmp, element);    }    int pop() {        // write your code here        int ret;        queue* pushtmp;        queue* tmp;        if(!IsQueueEmpty(queue1))        {            pushtmp = queue1;            tmp = queue2;        }        else        {            pushtmp = queue2;            tmp = queue1;        }        if(IsQueueEmpty(pushtmp))        {            cout<<stack is empty<<endl;        }        while(SizeOfQueue(pushtmp)!=1)        {            EnQueue(tmp,DeQueue(pushtmp));        }        ret = DeQueue(pushtmp);        return ret;    }