225. 用队列实现栈 Implement Stack using Queues

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.

Notes:

• 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).

public class MyStack {
        Queue<int> queue;
        public MyStack() {
            queue = new Queue<int>();
        }
        public void Push(int x) {
            queue.Enqueue(x);
        }
        public int Pop() {
            Queue<int> tempQueue = new Queue<int>();
            int count = queue.Count;
            for (int i = 0; i < count - 1; i++) {
                tempQueue.Enqueue(queue.Dequeue());
            }
            int top = queue.Dequeue();
            queue.Clear();
            count = tempQueue.Count();
            for (int i = 0; i < count; i++) {
                queue.Enqueue(tempQueue.Dequeue());
            }
            return top;
        }
        public int Top() {
            int[] arr = queue.ToArray();
            return arr[queue.Count - 1];
        }
        public bool Empty() {
            return queue.Count == 0;
        }
}

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