67. Add Binary

Very straightforward solution. I think the little challenge is the make the code clean and clever.

1:  class Solution {  
2:  public:  
3:    string addBinary(string a, string b) {  
4:      string s = "";  
5:      int c = 0, i = a.size()-1, j = b.size()-1;  
6:      while (i >= 0 || j >= 0 || c == 1) {  
7:        c += i >= 0 ? a[i--] - '0' : 0;  
8:        c += j >= 0 ? b[j--] - '0' : 0;  
9:        char t = c % 2 + '0';  
10:        s = t + s;  
11:        c /= 2;  
12:      }  
13:      return s;  
14:    }  
15:  };