Add Binary

class Solution {
public:
    string addBinary(string a, string b) {
        int n = a.size() > b.size() ? a.size() : b.size();
        reverse(a.begin(), a.end());
        reverse(b.begin(), b.end());
        
        int carry = 0;
        string result = "";
        for(int i=0; i<n; ++i)
        {
            int numa = i<a.size() ? (a[i] - ‘0‘) : 0;
            int numb = i<b.size() ? (b[i] - ‘0‘) : 0;
            int ret = (numa + numb + carry)%2;
            carry = (numa + numb + carry)/2;
            
            result.insert(0, to_string(ret));
        }
        
        if(carry)
            result.insert(0, to_string(carry));
            
        return result;
    }
};