【LeetCode43】 Multiply Strings

 1 public class LeetCode43 {
 2 public static void main(String[] args) {
 3     String num1="123";
 4     String num2="45";
 5     System.out.println(num1+"和"+num2+"相乘的结果是："+new Solution().multiply(num1, num2));
 6     }
 7 }
 8 
 9 class Solution {
10 public String multiply(String num1, String num2) {
11         int len1=num1.length(),len2=num2.length();
12         int[] result=new int[len1+len2];
13         for(int i=len1-1;i>=0;i--){
14             for(int j=len2-1;j>=0;j--){
15                 int mul=(num1.charAt(i)-'0')*(num2.charAt(j)-'0');
16                 int p1=i+j,p2=i+j+1;
17                 int sum=mul+result[p2];
18                 
19                 result[p1]+=sum/10;
20                 result[p2]=sum%10;
21             }
22         }
23         StringBuilder sb=new StringBuilder();
24         for(int e:result){
25             if(!(sb.length()==0&&e==0))//若最高位是0，去除
26                 sb.append(e);
27         }
28         return sb.length()==0?"0":sb.toString();
29     }
30 }