Add Binary Strings.cpp

class Solution {
  public:
    string addBinary(string& s1, string& s2) {
         reverse(s1.begin(), s1.end());
        reverse(s2.begin(), s2.end());
        string ans = "";
        char curr;
        int carry = 0, i = 0;
        while(carry > 0 || i < s1.length() || i < s2.length())
        {
            int sum = carry;
            if(i < s1.length())
            {
                if(s1[i] == '1')
                {
                    sum++;
                }
            }
            if(i < s2.length())
            {
                if(s2[i] == '1')
                {
                    sum++;
                }
            }
            if(sum == 0)
            {
                carry = 0;
                curr = '0';
            }
            else if(sum == 1)
            {
                carry = 0;
                curr = '1';
            }
            else if(sum == 2)
            {
                carry = 1;
                curr = '0';
            }
            else
            {
                carry = 1;
                curr = '1';
            }
            ans.push_back(curr);
            i++;
        }
        reverse(ans.begin(), ans.end());
        int ind = 0;
        while(ind < ans.length())
        {
            if(ans[ind] == '1')
            {
                break;
            }
            ind++;
        }
        return ans.substr(ind);
    }
};