LeetCode: Add Strings

反转再反转。。
 1 public class Solution {
 2     public String addStrings(String num1, String num2) {
 3         num1 = new StringBuffer(num1).reverse().toString();
 4         num2 = new StringBuffer(num2).reverse().toString();
 5         int c = 0;
 6         String ans = "";
 7         for (int i = 0; i < Math.min(num1.length(), num2.length()); i++) {
 8             c = (num1.charAt(i) - '0') + (num2.charAt(i) - '0') + c;
 9             ans = ans + (char)('0' + c % 10);
10             c /= 10;
11         }
12         
13         for (int i = Math.min(num1.length(), num2.length()); i < Math.max(num1.length(), num2.length()); i++) {
14             if (num1.length() < num2.length()) 
15                 c = (num2.charAt(i) - '0') + c;
16             else 
17                 c = (num1.charAt(i) - '0') + c;
18             ans += (char)('0' + c % 10);
19             c /= 10;
20         }
21         if (c > 0) 
22             ans += (char)('0' + c);
23         return new StringBuffer(ans).reverse().toString();
24     }
25 }