算法导论：打印回旋数；

 1 package org.warnier.zhang.exercises;
 2 
 3 public class Convolution {
 4     private int n;
 5     private int[][] array;
 6     private int number = 1;
 7 
 8     public Convolution(int n) {
 9         this.n = n;
10         array = new int[n][n];
11         init();
12     }
13 
14     private void init() {
15         for (int i = 0; i < n; i++) {
16             for (int j = 0; j < n; j++) {
17                 array[i][j] = 0;
18             }
19         }
20     }
21 
22     //逆时针方向回旋；
23     public void generateConvolutionNumber() {
24         //处理迭代“内圈”数字输出；
25         int a = 0;
26         int b = n -1 - a;
27         while (b >= a) {
28             //与正常的数组输出方向一致螺旋输出；
29             for (int i = a; i <= b; i++) {
30                 for (int j = a; j <= b; j++) {
31                     if (i != b && j == a) {
32                         array[i][j] = number++;
33                     }
34                     if (i == b && j != b) {
35                         array[i][j] = number++;
36                     }
37                 }
38             }
39             
40             //与正常的数组输出方向相反螺旋输出；
41             for (int i = b; i >= a; i--) {
42                 for (int j = b; j >= a; j--) {
43                     if (i != a && j == b) {
44                         array[i][j] = number++;
45                     }
46                     if (i == a && j != a) {
47                         array[i][j] = number++;
48                     }
49                 }
50             }
51             
52             a ++;
53             b = n -1 - a;
54         }
55         
56         //打个补丁：没能解决n为奇数的情况！（没有加上这句代码，中间的空格输出默认值0！）
57         if(n % 2 != 0){
58             array[n/2][n/2] = number;
59         }
60     }
61 
62     public void vprintf() {
63         for (int i = 0; i < n; i++) {
64             for (int j = 0; j < n; j++) {
65                 System.out.printf("%3d", array[i][j]);
66             }
67             System.out.println();
68         }
69     }
70 
71 }

 1 package org.warnier.zhang.exercises;
 2 
 3 public class ConvolutionTest {
 4 
 5     public static void main(String[] args) {
 6         Convolution convolution = new Convolution(5);
 7         convolution.generateConvolutionNumber();
 8         convolution.vprintf();
 9     }
10 
11 }
12 
13 结果：
14   1 16 15 14 13
15   2 17 24 23 12
16   3 18 25 22 11
17   4 19 20 21 10
18   5 6  7  8  9