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232. 用栈实现队列 Implement Queue using Stacks

2024-09-06 17:00:36   216人阅读

Implement the following operations of a queue using stacks.

  • push(x) -- Push element x to the back of queue.
  • pop() -- Removes the element from in front of queue.
  • peek() -- Get the front element.
  • empty() -- Return whether the queue is empty.
Notes:
  • You must use only standard operations of a stack -- which means only push to top, peek/pop from top, size, and is empty operations are valid.
  • Depending on your language, stack may not be supported natively. You may simulate a stack by using a list or deque (double-ended queue), as long as you use only standard operations of a stack.
  • You may assume that all operations are valid (for example, no pop or peek operations will be called on an empty queue).
  1. public class MyQueue {
  3.     public Stack<int> stack;

  5.     public MyQueue() {
  6.         stack = new Stack<int>();
  7.     }

  9.     public void Push(int x) {
  10.         stack.Push(x);
  11.     }

  13.     public int Pop() {
  14.         Stack<int> tempStack = new Stack<int>();
  15.         int count = stack.Count();
  16.         for (int i = 0; i < count; i++) {
  17.             tempStack.Push(stack.Pop());
  18.         }
  19.         int peek = tempStack.Pop();
  20.         stack.Clear();
  21.         count = tempStack.Count();
  22.         for (int i = 0; i < count; i++) {
  23.             stack.Push(tempStack.Pop());
  24.         }
  25.         return peek;
  26.     }

  28.     public int Peek() {
  29.         int[] arr = stack.ToArray();
  30.         return arr[stack.Count - 1];
  31.     }

  33.     public bool Empty() {
  34.         return this.stack.Count == 0;
  35.     }
  36. }





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232. 用栈实现队列 Implement Queue using Stacks


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