Restore IP Addresses

자연수로만 이루어진 문자열 s를 받는다.

이 문자열에서 유효한 IP 주소가 될 수 있는 것들을 추려내서 반환해야 한다.

유효한 IP 주소의 조건은 아래와 같다

A valid IP address consists of exactly four integers separated by single dots. 
Each integer is between 0 and 255 (inclusive) and cannot have leading zeros.
-
For example, "0.1.2.201" and "192.168.1.1" are valid IP addresses, 
but "0.011.255.245", "192.168.1.312" and "192.168@1.1" are invalid IP addresses.

class Solution {
public:
    vector<string> restoreIpAddresses(string s) {
        
        vector<string> result{};
        string temp{};
        _length = s.size();

        SearchDFS(0, s, result);

        return result;
    }

private:
    vector<string> _ip{};
    int _length{};

    void SearchDFS(int index, string& s, vector<string> &result)
    {
        if (_ip.size() == 4)
        {
            if (index == _length)
            {
                string temp{_ip[0] + '.' + _ip[1] + '.' + _ip[2] + '.' + _ip[3]};
                result.push_back(std::move(temp));
            }
            
            return;
        }


        for (int i = 1; i <= 3 && index + i <= _length; i++)
        {
            string temp = s.substr(index, i);
            if (255 < stoi(temp))
            {
                continue;
            }

            _ip.push_back(temp);
            SearchDFS(index + i, s, result);
            _ip.pop_back();

            if (temp == "0")
            {
                break;
            }
        }

        return;
    }
};