吸血鬼数字算法

 1         int[] startDigit = new int[4]; //start digit
 2         int[] productDigit = new int[4];   //product digit
 3         for (int num1 = 10; num1 <= 99; num1++){
 4             for (int num2 = num1; num2 <=99; num2++){
 5                 if ((num1 * num2) % 9 != (num1 + num2) % 9)
 6                     continue;
 7                 int product = num1 * num2;
 8                 startDigit[0] = num1 / 10;
 9                 startDigit[1] = num1 % 10;
10                 startDigit[2] = num2 / 10;
11                 startDigit[3] = num2 % 10;
12                 productDigit[0] = product / 1000;
13                 productDigit[1] = (product % 1000) / 100;
14                 productDigit[2] = product % 1000 % 100 /10;
15                 productDigit[3] = product % 1000 % 100 % 10;
16                 int count = 0;
17                 for (int x = 0; x < 4; x++){
18                     for (int y = 0; y < 4; y++){
19                         if (productDigit[x] == startDigit[y]){
20                             count++;
21                             productDigit[x] = -1;
22                             startDigit[y] = -2;
23                             if (count == 4)
24                                 System.out.println(num1 + " * " + num2 + ":" + product);
25                         }
26                     }
27                 }
28             }
29         }