使用队列实现栈(1)(Java) 

  1 class MyStack
  2 {
  3     private Queue q1;
  4     private Queue q2;
  5     
  6     public MyStack(int size)
  7     {
  8         this.q1 = new Queue(size);
  9         this.q2 = new Queue(size);
 10     }
 11     
 12     public boolean isFull()
 13     {
 14         return q1.isFull();
 15     }
 16     
 17     public boolean isEmpty()
 18     {
 19         return q1.isEmpty();
 20     }
 21     
 22     //时间复杂度: O(n)
 23     public void push(int k) throws Exception
 24     {
 25         if(this.isFull())
 26             throw new Exception("Overflow.");
 27         else
 28         {
 29             while(!this.q1.isEmpty())
 30                 this.q2.EnQueue(this.q1.DeQueue());
 31             this.q1.EnQueue(k);
 32             while(!this.q2.isEmpty())
 33                 this.q1.EnQueue(this.q2.DeQueue());
 34         }
 35     }
 36     
 37     //时间复杂度: O(1)
 38     public int pop() throws Exception
 39     {
 40         if(this.isEmpty())
 41             throw new Exception("Underflow");
 42         else
 43             return this.q1.DeQueue();
 44     }
 45 }
 46 
 47 class Queue
 48 {
 49     private int front;
 50     private int rear;
 51     private int[] a;
 52     
 53     public Queue(int size)
 54     {
 55         this.front = this.rear = 0;
 56         this.a = new int[size];
 57     }
 58     
 59     public boolean isFull()
 60     {
 61         return (this.rear + 1) % this.a.length == this.front;
 62     }
 63     
 64     public boolean isEmpty()
 65     {
 66         return this.rear == this.front;
 67     }
 68     
 69     public void EnQueue(int k) throws Exception
 70     {
 71         //该判断是冗余的
 72         /*if(this.isFull())
 73          * 
 74             throw new Exception("Overflow.");*/
 75         //else
 76         {
 77             this.a[this.rear] = k;
 78             this.rear = (this.rear + 1) % this.a.length;
 79         }
 80             
 81     }
 82     
 83     public int DeQueue() throws Exception
 84     {
 85         //该判断是冗余的
 86         /*if(this.isEmpty())
 87             throw new Exception("Underflow.");*/
 88         //else
 89         {
 90             int key = this.a[front];
 91             this.front = (this.front + 1) % this.a.length;
 92             return key;
 93         }
 94     }
 95     
 96     public int getLength()
 97     {
 98         return (this.rear - this.front + this.a.length) % this.a.length;
 99     }
100 }

 

posted @ 2019-04-11 16:03  Huayra  阅读(544)  评论(0)    收藏  举报