leetcode--Add Binary

Given two binary strings, return their sum (also a binary string).

For example,
a = "11"
b = "1"
Return "100".

[java] view plain copy

1. public class Solution {  
2.     public String addBinary(String a, String b) {  
3.         int i = a.length()-1;  
4.         int j = b.length()-1;  
5.         int flag = 0;  
6.         StringBuilder sb = new StringBuilder();  
7.         while(i>=0&&j>=0){  
8.             int t = a.charAt(i)-'0'+b.charAt(j)-'0'+flag;  
9.             flag = t>=2?1:0;           
10.             t = t%2;  
11.             sb.append(t);     
12.             i--;j--;  
13.         }  
14.         while(i>=0){  
15.             int t = a.charAt(i)-'0'+flag;  
16.             flag = t>=2?1:0;           
17.             t = t%2;  
18.             sb.append(t);  
19.             i--;  
20.         }  
21.         while(j>=0){  
22.             int t = b.charAt(j)-'0'+flag;  
23.             flag = t>=2?1:0;           
24.             t = t%2;  
25.             sb.append(t);  
26.             j--;  
27.         }  
28.         if(flag==1) sb.append(1);  
29.         return sb.reverse().toString();  
30.     }  
31. } 

原文链接http://blog.csdn.net/crazy__chen/article/details/46375901