LeetCode93——Restore IP Addresses

Given a string containing only digits, restore it by returning all possible valid IP address combinations.

For example: Given "25525511135",

return ["255.255.11.135", "255.255.111.35"]. (Order does not matter)

难度系数：中

实现

vector<string> restoreIpAddresses(string s, int index){    vector<string> vip;    if (index == 3) {        if (s.size() == 0 || s.size() > 3 || (s.size() > 1 && s[0] == '0'))            return vip;        int val = atoi(s.c_str());        if (val >= 0 && val <= 255) {            vip.push_back(s);        }        return vip;    } else {        for (int i = 1; i < 4 && i <= s.size(); i++) {            string tmp = s.substr(0, i);            if (i > 1 && s[0] == '0')                continue;            int val = atoi(tmp.c_str());            if (val >= 0 && val <= 255) {                vector<string> nextv = restoreIpAddresses(s.substr(i), index+1);                for (int k = 0; k < nextv.size(); ++k) {                    string ip(tmp);                    ip.append(".").append(nextv[k]);                    vip.push_back(ip);                }            }        }    }    return vip;}vector<string> restoreIpAddresses(string s) {    return restoreIpAddresses(s, 0);}