Leetcode•Nov 04, 2026

Validate IP Address

Hazrat Ali

Leetcode

A valid IPv4 address is an IP in the form "x1.x2.x3.x4" where 0 <= xi <= 255 and xi 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 "192.168@1.1" are invalid IPv4 addresses.

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

  • 1 <= xi.length <= 4
  • xi 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 xi.

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.

 

Example 1:

Input: queryIP = "172.16.254.1"
Output: "IPv4"
Explanation: This is a valid IPv4 address, return "IPv4".

Example 2:

Input: queryIP = "2001:0db8:85a3:0:0:8A2E:0370:7334"
Output: "IPv6"
Explanation: This is a valid IPv6 address, return "IPv6".

Example 3:

Input: queryIP = "256.256.256.256"
Output: "Neither"
Explanation: This is neither a IPv4 address nor a IPv6 address.

Solution
var validIPAddress = function(queryIP) {
    if (queryIP.includes(".")) {
        const parts = queryIP.split(".");

        if (parts.length !== 4) return "Neither";

        for (const part of parts) {
            if (
                part.length === 0 ||
                part.length > 3 ||
                (part.length > 1 && part[0] === '0') ||
                !/^\d+$/.test(part)
            ) {
                return "Neither";
            }

            const num = Number(part);

            if (num < 0 || num > 255) {
                return "Neither";
            }
        }

        return "IPv4";
    }

    if (queryIP.includes(":")) {
        const parts = queryIP.split(":");

        if (parts.length !== 8) return "Neither";

        for (const part of parts) {
            if (
                part.length < 1 ||
                part.length > 4 ||
                !/^[0-9a-fA-F]+$/.test(part)
            ) {
                return "Neither";
            }
        }

        return "IPv6";
    }

    return "Neither";
};
 

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