这个题做死我了

	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
     */
    auto isv4(string const& segement) -> bool {
        if (segement.empty()) return false;
        if (segement[0] == '0' && segement.length() > 1) return false;
        auto cur{0};
        for (auto ch : segement) {
            if (!isdigit(ch)) return false;
            cur = 10 * cur + (ch - '0');
        }
        return cur <= 0xff;
    }
    auto isv6(string const& segement) -> bool {
        if (segement.empty()) return false;
        if (segement.length() > 4) return false;
        if (segement.length() > 1 && segement.front() == '0' && segement[1] == '0') return false;
        auto cur{0};
        for (auto ch : segement) {
            if (isdigit(ch)) {
                cur = 16 * cur + (ch - '0');
            }else {
                ch = tolower(ch);
                cur = 16 * cur + (ch - 'a' + 10);
            }
        }
        return cur <= 0xffff;
    }
    string solve(string ip) {
        // write code here
        string ans;
        auto seg4{0}, seg6{0};
        enum Statu{alnum, other} statu{other};
        enum Type{v4, v6} type;
        size_t start{0};
        for (size_t i = 0; i < ip.length(); ++i) {
            if (auto ch = ip[i]; isalnum(ch)) {
                
                if (statu == other) {
                    start = i;
                    statu = alnum;
                }
                if (i == ip.length() - 1) {
                    if (type == v4) {
                        ++seg4;
                        if (!isv4(ip.substr(start))) {
                            ans = "Neither";
                        }
                    }else if (type = v6) {
                        ++seg6;
                        if (!isv6(ip.substr(start))) {
                            ans = "Neither";
                        }
                    }
                }
            }else {
                if (statu == alnum) {
                    statu = other;
                    if (ch == '.') {
                        type = v4;
                        ans = "IPv4";
                        ++seg4;
                        if (!isv4(ip.substr(start, i - start))) {
                            ans = "Neither";
                            break;
                        }
                    }else if (ch == ':') {
                        type = v6;
                        ans = "IPv6";
                        ++seg6;
                        if (!isv6(ip.substr(start, i - start))) {
                            ans = "Neither";
                            break;
                        }
                    }
                }
            }
        }
        if (statu == other) ans = "Neither";
        if (type == v4 && seg4 != 4) ans = "Neither";
        if (type == v6 && seg6 != 8) ans = "Neither";
        
        return ans;
    }
    
};