Java学习-练习1

题目描述：

　　吸血鬼数字是指位数为偶数的数字，可以由一对数字相乘而得到，

而这对数字各包含乘积的一半位数的数字，其中最初的数字中可以

选取的数字可以任意排序，以两个0结尾的数字是不允许的，例如，下

面的数字都是吸血鬼数字：

1260=21*60

1827=21*87

2187=27*81

编写一个程序，找出4位数的所有吸血鬼数字。

 package chapter3_Ex10;

 public class Vampire {

     public static void main(String[] args){
         int[] startDigit=new int[4];
         int[] productDigit=new int[4];
         for(int num1=10;num1<100;++num1){
             for(int num2=num1;num2<100;++num2){
                 if((num1*num2)%9 != (num1+num2)%9)
                     continue;
                 int product=num1*num2;
                 startDigit[0]=num1/10;
                 startDigit[1]=num1%10;
                 startDigit[2]=num2/10;
                 startDigit[3]=num2%10;
                 productDigit[0]=product/1000;
                 productDigit[1]=product%1000/100;
                 productDigit[2]=product%1000%100/10;
                 productDigit[3]=product%1000%100%10;
                 int count=0;
                 for(int i=0;i<4;++i){
                     for(int j=0;j<4;j++){
                         if(startDigit[i]==productDigit[j]){
                             ++count;
                             startDigit[i]=-1;
                             productDigit[j]=-2;

                         }
                     }
                 }
                 if(count==4){
                     System.out.println(num1+" * "+num2+" = "+product);
                 }
             }
         }
     }
 }

运行结果：

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