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Validate IP Address

Difficulty: Medium

Problem Description

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.

Key Insights

  • A valid IPv4 address consists of four octets separated by dots (.), where each octet is a number between 0 and 255 and cannot have leading zeros.
  • A valid IPv6 address consists of eight groups of four hexadecimal digits separated by colons (:), where each group can have leading zeros.
  • Input strings can contain only alphanumeric characters and the characters '.' and ':'.
  • The validation process involves parsing the string and checking the format and ranges of the components.

Space and Time Complexity

Time Complexity: O(n), where n is the length of the input string. Each character is processed a limited number of times. Space Complexity: O(1), as we use a fixed amount of space for variables, regardless of the input size.

Solution

To solve the problem, we will use two separate validation functions, one for IPv4 and one for IPv6. The IPv4 function will split the input string by '.', check the count of segments, validate each segment as an integer between 0 and 255, and ensure no segment has leading zeros. The IPv6 function will split the input string by ':', check the count of segments, and validate each segment to ensure it is a valid hexadecimal string of length between 1 and 4. Finally, based on the validations, we return the appropriate result.

Code Solutions

def validateIP(queryIP: str) -> str:
    def is_valid_ipv4(segment: str) -> bool:
        if not segment.isdigit() or len(segment) == 0 or len(segment) > 3:
            return False
        if segment[0] == '0' and len(segment) > 1:  # leading zero
            return False
        return 0 <= int(segment) <= 255

    def is_valid_ipv6(segment: str) -> bool:
        if len(segment) < 1 or len(segment) > 4:
            return False
        for char in segment:
            if not (char.isdigit() or ('a' <= char.lower() <= 'f')):
                return False
        return True

    if queryIP.count('.') == 3:  # Potential IPv4
        segments = queryIP.split('.')
        if all(is_valid_ipv4(segment) for segment in segments):
            return "IPv4"
    elif queryIP.count(':') == 7:  # Potential IPv6
        segments = queryIP.split(':')
        if all(is_valid_ipv6(segment) for segment in segments):
            return "IPv6"

    return "Neither"
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