LeetCode OJ：Add Binary（二进制相加）

 1 class Solution {
 2 public:
 3     string addBinary(string a, string b) {
 4         reverse(a.begin(), a.end());
 5         reverse(b.begin(), b.end());
 6         int len1 = a.length();
 7         int len2 = b.length();
 8         string result;
 9         int flag ,val;
10         flag = val = 0;
11         int i;
12         for(i = 0; i < len1 && i < len2; ++i){
13             val = (a[i] - ‘0‘) + (b[i] - ‘0‘) + flag;
14             result.append(1, val % 2 + ‘0‘);
15             flag = val/2;
16         }
17         while (i < len1) {
18             val = a[i] - ‘0‘+ flag;
19             result.append(1, val % 2 + ‘0‘);
20             flag = val/2;
21             ++i;
22         }
23         while (i < len2 ){
24             val = b[i] - ‘0‘+ flag;
25             result.append(1, val % 2 + ‘0‘);
26             flag = val/2;
27             ++i;
28         }
29         cout << "flag " << flag << endl;
30         if(flag != 0)
31             result.append(1, ‘1‘);
32         reverse(result.begin(), result.end());
33         return result;
34     }
35 };