93. Restore IP Addresses

class Solution {
public:
    vector<string> restoreIpAddresses(string s) {
        return getStrs(3, s);
    }
    
    vector<string> getStrs(int n, string s){
        int len = s.length();
        vector<string> res;
        if(n > len - 1 ) return res;
        if(n == 0){
            int value = 0;
            for(int i=0; i<len; i++){
                value = value * 10 + s[i] - ‘0‘;
            }
            if(s[0] == ‘0‘ && len == 1){
                res.push_back(s);
            }
            if(s[0]!=‘0‘ && value >=0 && value<=255){
                res.push_back(s);
            }
            return res;
        }
        string str = "";
        int value = 0;
        for(int i=0; i<len && i<3; i++){
            str += s[i];
            value = 10 * value + (s[i] - ‘0‘);
            if(value >= 0 && value <= 255){
                string temp = str + ".";
                string nextStr = "";
                for(int j=i+1; j<len; j++)
                    nextStr += s[j];
                vector<string> nextStrs = getStrs(n-1, nextStr);
                for(int j=0; j<nextStrs.size(); j++){
                    temp += nextStrs[j];
                    res.push_back(temp);
                    temp = str + ".";
                }
            }
            if(i==0 && s[i] == ‘0‘) break;
        }
        return res;
    }
};