剑指 Offer 09. 用两个栈实现队列

  1. class CQueue {
  3.     Deque<Integer> stack1;
  4.     Deque<Integer> stack2;
  6.     public CQueue() {
  7.         stack1 = new LinkedList<Integer>();
  8.         stack2 = new LinkedList<Integer>();
  9.     }
  11.     public void appendTail(int value) {
  12.         stack1.push(value);
  13.     }
  15.     public int deleteHead() {
  16.         // 如果第二个栈为空
  17.         if (stack2.isEmpty()) {
  18.             while (!stack1.isEmpty()) {
  19.                 stack2.push(stack1.pop());
  20.             }
  21.         } 
  22.         if (stack2.isEmpty()) {
  23.             return -1;
  24.         } else {
  25.             int deleteItem = stack2.pop();
  26.             return deleteItem;
  27.         }
  28.     }
  30. // 作者：LeetCode-Solution
  31. // 链接：https://leetcode-cn.com/problems/yong-liang-ge-zhan-shi-xian-dui-lie-lcof/solution/mian-shi-ti-09-yong-liang-ge-zhan-shi-xian-dui-l-3/
  32. }