题解 | #验证IP地址#

模拟题

class Solution {
public:
    /**
     * 验证IP地址
     * @param IP string字符串 一个IP地址字符串
     * @return string字符串
     */
    string solve(string IP) {
        // write code here
        const string IPS[3] = {"IPv4", "IPv6", "Neither"};
        int idx = 2;
        vector<string> vec;
        int n = IP.length();
        string str;
        char flag = '#';
        for(int i = 0; i < n; i ++){
            if(i > 0){
                if(IP[i] == '.' || IP[i] == ':'){
                    if(IP[i - 1] == IP[i]) return IPS[2];
                }
            }
            if(IP[i] == '.' || IP[i] == ':'){
                vec.push_back(str);
                str = "";
                if(flag == '#') flag = IP[i];
                else{
                    if(flag != IP[i]) return IPS[2];
                }
            }else str += IP[i];
        }
        vec.push_back(str);
        if(flag == '.'){
            if(vec.size() != 4 || !isIPv4(vec)) return IPS[2];
            else return IPS[0];
        }else{
            if(vec.size() != 8 || !isIPv6(vec)) return IPS[2];
            else return IPS[1];
        }
        return IPS[2];
    }
    bool isIPv4(const vector<string>& vec){
        for(int i = 0; i < 4; i ++){
            if(vec[i].length() > 1 && vec[i][0] == '0') return false;
            if(stoi(vec[i]) >= 256) return false;
        }
        return true;
    }
    bool isIPv6(const vector<string>& vec){
        unordered_set<char> ust;
        for(char ch = '0'; ch <= '9'; ch ++) ust.insert(ch);
        for(char ch = 'a'; ch <= 'f'; ch ++) ust.insert(ch);
        for(char ch = 'A'; ch <= 'F'; ch ++) ust.insert(ch);
        for(int i = 0; i < 8; i ++){
            if(vec[i].length() > 4) return false;
            for(int j = 0; j < vec[i].length(); j ++){
                if(ust.count(vec[i][j]) == 0) return false;
            }
        }
        return true;
    }
};