class MyStack {
//定义一个队列
Queue<Integer> queue = new LinkedList<>();
/** Initialize your data structure here. */
public MyStack() {
}
/** Push element x onto stack. */
//队列是先进先出，栈为先进后出，用队列模拟栈时，添加一个元素是在队列的末尾，弹出一个元素是在队头
//此时把该元素前面的元素全部出队，该元素就到了队首，其余元素再进队，即为一个栈先进后出的顺序
public void push(int x) {
queue.add(x);
int count = queue.size();
while(count > 1){
queue.add(queue.remove());
count--;
}
}
/** Removes the element on top of the stack and returns that element. */
public int pop() {
return queue.remove();
}
/** Get the top element. */
public int top() {
return queue.peek();
}
/** Returns whether the stack is empty. */
public boolean empty() {
return queue.isEmpty();
}
}
/**
* Your MyStack object will be instantiated and called as such:
* MyStack obj = new MyStack();
* obj.push(x);
* int param_2 = obj.pop();
* int param_3 = obj.top();
* boolean param_4 = obj.empty();
*/
