剑指09 用两个栈实现队列

  1. class CQueue {
  2.     private Deque<Integer> stack1;
  3.     private Deque<Integer> stack2;
  5.     public CQueue() {
  6.         stack1 = new LinkedList<Integer>();
  7.         stack2 = new LinkedList<Integer>();
  8.     }
  10.     public void appendTail(int value) {
  11.         stack1.push(value);
  12.     }
  14.     public int deleteHead() {
  15.         if (stack1.isEmpty() && stack2.isEmpty())
  16.             return -1;
  18.         if (stack2.isEmpty())
  19.             while (!stack1.isEmpty())
  20.                 stack2.push(stack1.pop());
  22.         return stack2.pop();
  23.     }
  24. }
  26. /**
  27.  * Your CQueue object will be instantiated and called as such:
  28.  * CQueue obj = new CQueue();
  29.  * obj.appendTail(value);
  30.  * int param_2 = obj.deleteHead();
  31.  */