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 backpeek/pop from frontsize, 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).
  1. public class MyStack {
  2. Queue<int> queue;
  3. public MyStack() {
  4. queue = new Queue<int>();
  5. }
  6. public void Push(int x) {
  7. queue.Enqueue(x);
  8. }
  9. public int Pop() {
  10. Queue<int> tempQueue = new Queue<int>();
  11. int count = queue.Count;
  12. for (int i = 0; i < count - 1; i++) {
  13. tempQueue.Enqueue(queue.Dequeue());
  14. }
  15. int top = queue.Dequeue();
  16. queue.Clear();
  17. count = tempQueue.Count();
  18. for (int i = 0; i < count; i++) {
  19. queue.Enqueue(tempQueue.Dequeue());
  20. }
  21. return top;
  22. }
  23. public int Top() {
  24. int[] arr = queue.ToArray();
  25. return arr[queue.Count - 1];
  26. }
  27. public bool Empty() {
  28. return queue.Count == 0;
  29. }
  30. }






posted @ 2017-03-02 22:53  xiejunzhao  阅读(264)  评论(0编辑  收藏  举报