大数乘法

 1 import java.util.Scanner;
 2 
 3 /**
 4  * 大整数相乘
 5  *
 6  */
 7 
 8 public class bigNumberMulti {
 9 
10     static char[] reverse(char[] ch){//字符反转，即123转为321
11         int length = ch.length;
12         char[] temp = new char[length];
13         for(int i=0;i<length;i++){
14             temp[length-1-i] = ch[i];            
15         }
16         
17         
18         return temp;
19     }
20     static void multi(char[] chr1,char[] chr2){//乘法运算
21         int n = chr1.length;
22         int m = chr2.length;
23         chr1 = reverse(chr1);
24         chr2 = reverse(chr2);
25         int [] result = new int [m+n];
26         for(int i=0;i<n;i++){        //暂时不处理进位，将i+j位的数累加起来，然后进行统一进位处理
27             for(int j=0;j<m;j++){
28                 int temp = (chr1[i]-48)*(chr2[j]-48);
29                 result[i+j] += temp;
30             }
31         }
32         
33         for(int i=0;i<m+n-1;i++){    //处理进位
34             int temp = result[i]/10;
35             result[i] = result[i]%10;
36             result[i+1] += temp;
37         }
38         int location = 0;            //记录最高位的位置
39         for(int i=m+n-1;i>=0;i--){    //找到最高位的位置
40             if(result[i]!=0){
41                 location = i;
42                 break;
43             }
44         }
45         for(int i=location;i>=0;i--){ //打印结果
46             System.out.print(result[i]);
47         }
48         
49     }
50     
51     public static void main(String[] args) {
52         // TODO Auto-generated method stub
53         Scanner  sc = new Scanner(System.in);
54         char [] chr1 = sc.next().toCharArray();
55         char [] chr2 = sc.next().toCharArray();
56         multi(chr1, chr2);
57         
58     }
59 
60 }