Leetcode 之Add Binary（29）

string addBinary(string a, string b)
      {
          string result;

          int len = a.size() > b.size() ? a.size() : b.size();

          reverse(a.begin(), a.end());
          reverse(b.begin(), b.end());

          int carry = 0;

          for (int i = 0; i < len; i++)
          {
              int ai = i < a.size() ? a[i] - ‘0‘ : 0;
              int bi = i < b.size() ? b[i] - ‘0‘ : 0;

              int val = (ai + bi + carry) % 2;
              carry = (ai + bi + carry) / 2;

              result.insert(result.begin(), val + ‘0‘);
          }

          if (carry == 1)result.insert(result.begin(), ‘1‘);
          return result;

      }