232.用栈实现队列【简单】

1、思路

1、用两个栈来实现队列
2、一个栈是进栈inStack
3、一个栈是出栈outStack
4、其中我们自定义一个方法pushToOutStack()
5、这个方法的作用是将inStack中的数据放到outStack中
6、在peek()/pop()方法调用时，需要添加该自定义方法。用来保持队列的先进先出要求。

class MyQueue {
    Stack inStack ;
    Stack outStack;

    public MyQueue() {
        inStack = new Stack();
        outStack = new Stack();
    }

    public void push(int x) {
        inStack.push(x);
    }

    public int pop() {
        if(outStack.isEmpty()){
            pushToOutStack();
        }
        return outStack.pop();
    }

    public int peek() {
        if(outStack.isEmpty()){
            pushToOutStack();
        }
        return outStack.peek();

    }

    public boolean empty() {
        boolean loop;
        if(inStack.isEmpty() && (outStack.isEmpty())){
            loop =true;
        }else{
            loop =false;
        }
        return loop;

    }

    public void pushToOutStack(){
        if(!inStack.isEmpty()){
            while(!inStack.isEmpty()){
                outStack.push(inStack.pop());
            }
        }
    }

}