67. 二进制求和

class Solution {
    public:
    string addBinary(string a, string b) {
        std::string result;
        if(a.size() == 0 || b.size() == 0) {
            return a.size() == 0? b:a;
        }
        int jinwei = 0;
        for(int i = a.size()-1, j = b.size()-1; i >=0 || j >= 0; --j, --i) {
            int sum = jinwei;
            sum += i >= 0? a[i]-'0':0;
            sum += j >= 0? b[j]-'0':0;
            result = to_string(sum%2) + result;
            jinwei = sum/2;
        }
        result = (jinwei == 1? "1":"") + result;
        //result += (jinwei == 1? "1":"");
        //reverse(result.begin(), result.end());
        return std::move(result);
    }
};