思科校招算法-验证IP地址-Leetcode.468

Quest

Given a string queryIP, return "IPv4" if IP is a valid IPv4 address, "IPv6" if IP is a valid IPv6 address or "Neither" if IP is not a correct IP of any type.

A valid IPv4 address is an IP in the form "x1.x2.x3.x4" where 0 <= xi <= 255 and x_i cannot contain leading zeros. For example, "192.168.1.1" and "192.168.1.0" are valid IPv4 addresses while "192.168.01.1", "192.168.1.00", and "[email protected]" are invalid IPv4 addresses.

A valid IPv6 address is an IP in the form "x1:x2:x3:x4:x5:x6:x7:x8" where:

• 1 <= x_i.length <= 4
• x_i is a hexadecimal string which may contain digits, lowercase English letter ('a' to 'f') and upper-case English letters ('A' to 'F').
• Leading zeros are allowed in x_i.

For example, "2001:0db8:85a3:0000:0000:8a2e:0370:7334" and "2001:db8:85a3:0:0:8A2E:0370:7334" are valid IPv6 addresses, while "2001:0db8:85a3::8A2E:037j:7334" and "02001:0db8:85a3:0000:0000:8a2e:0370:7334" are invalid IPv6 addresses.

---

#include <algorithm>
#include <array>
#include <cctype>
#include <cstdlib>
#include <iostream>
#include <string>
#include <vector>

using namespace std;

class Solution {

private:
    static constexpr size_t MAX_LENGTH = 39;
    string                  strFail    = "Neither";
    string                  strIPv4    = "IPv4";
    string                  strIPv6    = "IPv6";

    bool checkLength(const string &queryIP) {
        if (queryIP.length() > MAX_LENGTH) {
            return false;
        }
        return true;
    }

    bool checkIPv4Digits(const string &digits) {
        // length check
        if (digits.empty() || digits.length() > 3) {
            return false;
        }

        // leading zero
        if (digits.length() != 1 && digits.at(0) == '0') { //  digits.starts_with('0')
            return false;
        }

        // non digit characters
        for (auto &c: digits) {
            if (isdigit(c) == false) {
                return false;
            }
        }

        // value > 255
        if (stoi(digits, nullptr, 10) > 255) {
            return false;
        }

        return true;
    }

    bool checkIPv6Digits(const string &digits) {
        // length check
        if (digits.empty() || digits.length() > 4) {
            return false;
        }


        // non digit characters
        if (digits.find_first_not_of("0123456789abcdefABCDEF", 0) != string::npos) {
            return false;
        }

        return true;
    }

    bool checkIPv4(string queryIP) {
        string         delim = ".";
        size_t         pos   = 0;
        string    token;
        vector<string> digits;

        while ((pos = queryIP.find(delim)) != string::npos) {
            token = queryIP.substr(0, pos);
            digits.push_back(token);
            queryIP.erase(0, pos + delim.length());
        }
        token = queryIP;
        digits.push_back(token);

        for (auto &i: digits) {
            if (checkIPv4Digits(i) == false) {
                return false;
            }
        }

        return true;
    }

    bool checkIPv6(string queryIP) {
        string         delim = ":";
        size_t         pos   = 0;
        string    token;
        vector<string> digits;

        while ((pos = queryIP.find(delim)) != string::npos) {
            token = queryIP.substr(0, pos);
            digits.push_back(token);
            queryIP.erase(0, pos + delim.length());
        }
        token = queryIP;
        digits.push_back(token);

        for (auto &i: digits) {
            if (checkIPv6Digits(i) == false) {
                return false;
            }
        }
        return true;
    }


public:
    string validIPAddress(string queryIP) {
        if (checkLength(queryIP) == false) {
            return strFail;
        }

        if (count(queryIP.begin(), queryIP.end(), '.') == 3) {
            if (checkIPv4(queryIP) == true) {
                return strIPv4;
            }
        }
        else if (count(queryIP.begin(), queryIP.end(), ':') == 7) {
            if (checkIPv6(queryIP) == true) {
                return strIPv6;
            }
        }

        return strFail;
    }
};

template <typename T, typename... N>
auto make_array(N &&...args) -> std::array<T, sizeof...(args)> {
    return {std::forward<N>(args)...};
}

int main() {
    Solution s;
    auto     inputs = make_array<string>("172.16.254.1", "2001:0db8:85a3:0:0:8A2E:0370:7334", "256.256.256.256");

    for (auto &testCase: inputs) {
        cout << s.validIPAddress(testCase) << endl;
    }

    return EXIT_SUCCESS;
}

Refers

• https://stackoverflow.com/questions/14265581/parse-split-a-string-in-c-using-string-delimiter-standard-c
• https://stackoverflow.com/questions/8899069/how-to-find-if-a-given-string-conforms-to-hex-notation-eg-0x34ff-without-regex
• https://stackoverflow.com/questions/791982/determine-if-a-string-is-a-valid-ipv4-address-in-c