restore_ip_addresses.cpp

//slow approach. I believe its related with concatenation on the fly. += 
class Solution {
    void getIPAddresses(vector<string> &temp, vector<string> &IPs, string &s, int index) {
        if(index == s.length() && temp.size() == 4) {
            string validIP = temp[0] + '.' + temp[1] + '.' + temp[2] + '.' + temp[3] ;
            IPs.push_back(validIP);
            return;
        }

        string tempStr = "";
        for(int i = index ; i< s.length() && temp.size() < 4; i++) {
            if(s[i] - '0' > 9) {
                continue;
            }
            tempStr += s[i];
            int tempInt = stoi(tempStr);
            if(0 <= tempInt && tempInt <= 255) {
                temp.push_back(tempStr);
                getIPAddresses(temp, IPs, s, i+1);
                temp.pop_back();
            }
            if(tempInt <= 0 || tempInt > 255) {
                break;
            }
        }
    }

public:
    vector<string> restoreIpAddresses(string s) {
        vector<string> IPs;
        vector<string> temp;
        getIPAddresses(temp, IPs, s, 0);
        return IPs;
    }
    
  
};