class Solution {
public:
string addBinary(string a, string b) {
string result = "";
int c = 0;
int i = a.size() - 1;
int j = b.size() - 1;
while(i >= 0 || j >= 0 || c == 1) {
c += i >= 0 ? a[i--] - '0' : 0;
c += j >= 0 ? b[j--] - '0' : 0;
result = char(c%2 + '0') + result;
c /= 2;
}
return result;
}
};