Add Binary

 Given two binary strings a and b, return their sum as a binary string.

 

        int i = a.size() - 1;
        int j = b.size() - 1;
        int carry=0;
        string result = "";
        while (i >= 0 || j >= 0 ) {
            int sum=carry;
            if (i >= 0 ) sum+=a[i--]-'0'; // its given in string to convert in integer we subtract it with '0'
            if (j >= 0 ) sum+=b[j--]-'0';
            carry=sum>1?1:0;
            result+=to_string(sum%2);
        }
        if(carry)  result+=to_string(carry);//convert int to string
        reverse(result.begin(),result.end());
        return result;