LeetCode.232 Implement Queue using Stacks

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 2019/06/05   Share

https://leetcode.com/problems/implement-queue-using-stacks/submissions/

题意

用Stack来实现队列的功能
解法

采用两个Stack sPush和sPop来实现，push时加进sPush，pop时判断sPop是否为空，否则将sPush中的所有元素加进sPop，再从sPop中pop

class MyQueue {

  Stack<Integer> push = new Stack<>();
  Stack<Integer> pop = new Stack<>();

  /**
   * Initialize your data structure here.
   */
  public MyQueue() {

  }

  /**
   * Push element x to the back of queue.
   */
  public void push(int x) {
      push.push(x);
  }

  /**
   * Removes the element from in front of queue and returns that element.
   */
  public int pop() {
      if (pop.isEmpty()) {
          while (!push.isEmpty()) {
              pop.push(push.pop());
          }
      }
      return pop.pop();
  }

  /**
   * Get the front element.
   */
  public int peek() {
      if (pop.isEmpty()) {
          while (!push.isEmpty()) {
              pop.push(push.pop());
          }
      }
      return pop.peek();
  }

  /**
   * Returns whether the queue is empty.
   */
  public boolean empty() {
      return push.isEmpty() && pop.isEmpty();
  }
}

原文作者：Matteo

原文链接：http://tlzxsun.github.io/2019/06/05/LeetCode-232-Implement-Queue-using-Stacks/

发表日期：June 5th 2019, 10:56:22 am

更新日期：June 5th 2019, 10:56:23 am