LeetCode-Restore IP Addresses

哎，写代码太不专注了，

还是头脑和注意力不够集中，

需要多在脑子里面磨练，

另外写程序的思维方式还比较土，

总喜欢单独考虑很多特殊情况，导致代码看起来很繁琐，

需要多看别人的代码好好学习如何写得简洁短小；

class Solution {
public:
    vector<string> restoreIpAddresses(string s) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<string> res;
        if (s.empty() || s.size() < 4 || s.size() > 12) {
            return res;
        }
        vector<string> ip;
        get(res, ip, s, 0, 0);
        return res;
    }
    void get(vector<string> &res, vector<string> &ip, string &s, int p, int num) {
        if (num == 3) {
            if (s.size() - p > 3) {
                return;
            }
            if (s[p] == '0' && p != s.size() - 1) {
                return;
            }
            int n = 0;
            for (int i = p; i < s.size(); ++i) {
                n = n * 10 + s[i] - '0';
            }
            if (n > 255) {
                return;
            }
            string ipstr = s.substr(p, s.size() - p + 1);
            string ret = ip[0] + "." + ip[1] + "." + ip[2] + "." + ipstr;
            res.push_back(ret);
            return;
        }
        if (s[p] == '0') {
            ip.push_back(s.substr(p, 1));
            int len = s.size() - p - 1;
            int t = 3 - num;
            if (len < t || len > 3 * t) {
                return;
            }
            get(res, ip, s, p + 1, num + 1);
        }
        else {
            for (int i = 0; i < 3; ++i) {
                vector<string> nvec = ip;
                nvec.push_back(s.substr(p, i + 1));
                int len = s.size() - p - 1 - i;
                int t = 3 - num;
                if (len < t || len > 3 * t) {
                    continue;
                }
                if (i == 2) {
                    int temp = 100 * (s[p] - '0') + 10 * (s[p + 1] - '0') + (s[p + 2] - '0');
                    if (temp > 255) {
                        continue;
                    }
                }
                get(res, nvec, s, p + i + 1, num + 1);
            }
        }
    }
};