【LeetCode415】Add Strings

 1 public class LeetCode415 {
 2     public static void main(String[] args) {
 3         String a="1",b="9";
 4         System.out.println(a+"和"+b+"相加的结果是："+new Solution().addStrings(a, b));
 5     }
 6 }
 7 class Solution {
 8     public String addStrings(String num1, String num2) {
 9         int len1=num1.length(),len2=num2.length();
10         int i=len1-1,j=len2-1;
11         int carry=0;
12         StringBuilder sb=new StringBuilder();
13         while(i>=0||j>=0){
14             int sum=carry;
15             if(i>=0) sum+=num1.charAt(i--)-'0';
16             if(j>=0) sum+=num2.charAt(j--)-'0';
17             sb.append(sum%10);
18             carry=sum/10;
19         }
20         if(carry==1) sb.append(carry);
21         return (sb.length()==0?"0":sb.reverse().toString());
22     }
23 }