用两个栈实现一个队列

Posted 2020-10-16 梵高先生

【题目】两个栈实现一个队列

 

 1 import java.util.Stack;
 2 
 3 public class Main {
 4 
 5     public static void main(String[] args) {
 6 
 7         Stack<Integer> stack1 = new Stack<Integer>();
 8         Stack<Integer> stack2 = new Stack<Integer>();
 9 
10         MyQueue myQueue = new MyQueue(stack1, stack2);
11 
12         myQueue.appendTail(1);
13         myQueue.appendTail(2);
14         myQueue.appendTail(3);
15         System.out.println(myQueue.deleteHead());
16         System.out.println(myQueue.deleteHead());
17         myQueue.appendTail(4);
18         myQueue.appendTail(5);
19         System.out.println(myQueue.deleteHead());
20         System.out.println(myQueue.deleteHead());
21         System.out.println(myQueue.deleteHead());
22         System.out.println(myQueue.deleteHead());
23 
24     }
25 
26 }
27 
28 class MyQueue {
29 
30     private Stack<Integer> stack1;
31     private Stack<Integer> stack2;
32 
33     public MyQueue(Stack<Integer> stack1, Stack<Integer> stack2) {
34         this.stack1 = stack1;
35         this.stack2 = stack2;
36     }
37 
38     public Boolean appendTail(Integer num) {
39         Boolean result = false;
40         if (null != num) {
41             stack1.push(num);
42             result = true;
43         }
44         return result;
45     }
46 
47     public Integer deleteHead() {
48         if (!stack2.isEmpty()) {
49             return stack2.pop();
50         }
51 
52         if (stack2.isEmpty() && !stack1.isEmpty()) {
53             int length = stack1.size();
54             for (int i = 0; i < length; i++) {
55                 Integer temp = stack1.pop();
56                 stack2.push(temp);
57             }
58             return stack2.pop();
59         }
60 
61         return null;
62     }
63 
64     public Stack<Integer> getStack1() {
65         return stack1;
66     }
67 
68     public void setStack1(Stack<Integer> stack1) {
69         this.stack1 = stack1;
70     }
71 
72     public Stack<Integer> getStack2() {
73         return stack2;
74     }
75 
76     public void setStack2(Stack<Integer> stack2) {
77         this.stack2 = stack2;
78     }
79 
80 }