Implement the following operations of a stack using queues.

push(x) -- Push element x onto stack.

pop() -- Removes the element on top of the stack.

top() -- Get the top element.

empty() -- Return whether the stack is empty.

Example:

MyStack stack = new MyStack();

stack.push(1);
stack.push(2);
stack.top();   // returns 2
stack.pop();   // returns 2
stack.empty(); // returns false

• You must use only standard operations of a queue -- which means only push to back, peek/pop from front, size, and is empty operations are valid.
• Depending on your language, queue may not be supported natively. You may simulate a queue by using a list or deque (double-ended queue), as long as you use only standard operations of a queue.
• You may assume that all operations are valid (for example, no pop or top operations will be called on an empty stack).

Tags: Queue, Stack

只使用队列的标准操作来实现栈，这些操作仅仅包括push to back, peek/pop from front, size, is empty

主要体现为实现四个函数

• push(x) 在栈的末尾增加元素
• pop() 在栈顶删除元素
• peek() 查看栈顶元素
• empty() 查看是否是空栈

定义结构体MyStack,包含两个元素，分别是入队列enqueue和出队列dequeue,所有入栈数据都先存入enquequ, 所有的出栈数据都来自dequeue

type MyStack struct {
  enqueue []int
  dequeue []int
}

如果你同我一样热爱数据结构、算法、LeetCode，可以关注我 GitHub 上的 LeetCode 题解：awesome-golang-letcode