67. Add Binary

class Solution {
public:
    string addBinary(string a, string b) {
       int n = a.size()-1;
       int m = b.size()-1;
       int carry=0;
       string s;

       while(n >= 0 || m >= 0)
       {
           if(n >= 0 && m >= 0)
           {
            int val = ((a[n] - '0') + (b[m] - '0') + carry)%2;
            carry=((a[n] - '0') + (b[m] - '0') + carry)/2;
            s+=(val + '0');
            n--; m--;
           }

           else if(n >= 0)
           {
            int val = ((a[n] - '0') + carry)%2;
            carry=((a[n] - '0') + carry)/2;
            s+=(val + '0');
            n--;
           }

           else
           {
            int val = ((b[m] - '0') + carry)%2;
            carry=((b[m] - '0') + carry)/2;
            s+=(val + '0');
            m--;
           }
         
       }

       if(carry > 0)
          s.push_back(carry+'0');

       reverse(s.begin(), s.end());

       return s;
    }
};