validate-ip-address.py

# Time:  O(1)
# Space: O(1)

# In this problem, your job to write a function to check whether a input string 
# is a valid IPv4 address or IPv6 address or neither.
#
# IPv4 addresses are canonically represented in dot-decimal notation,
# which consists of four decimal numbers, each ranging from 0 to 255, separated by dots ("."), e.g.,172.16.254.1;
#
# Besides, you need to keep in mind that leading zeros in the IPv4 is illegal.
# For example, the address 172.16.254.01 is illegal.
#
# IPv6 addresses are represented as eight groups of four hexadecimal digits,
# each group representing 16 bits. The groups are separated by colons (":").
# For example, the address 2001:0db8:85a3:0000:0000:8a2e:0370:7334 is a legal one.
# Also, we could omit some leading zeros among four hexadecimal digits and
# some low-case characters in the address to upper-case ones,
# so 2001:db8:85a3:0:0:8A2E:0370:7334 is also a valid IPv6 address(Omit leading zeros and using upper cases).
#
# However, we don't replace a consecutive group of zero value with a single empty group
# using two consecutive colons (::) to pursue simplicity.
# For example, 2001:0db8:85a3::8A2E:0370:7334 is an invalid IPv6 address.
#
# Besides, you need to keep in mind that extra leading zeros in the IPv6 is also illegal.
# For example, the address 02001:0db8:85a3:0000:0000:8a2e:0370:7334 is also illegal.
#
# Note: You could assume there is no extra space in the test cases and
# there may some special characters in the input string.
#
# Example 1:
# Input: "172.16.254.1"
#
# Output: "IPv4"
#
# Explanation: This is a valid IPv4 address, return "IPv4".
# Example 2:
# Input: "2001:0db8:85a3:0:0:8A2E:0370:7334"
#
# Output: "IPv6"
#
# Explanation: This is a valid IPv6 address, return "IPv6".
# Example 3:
# Input: "256.256.256.256"
#
# Output: "Neither"
#
# Explanation: This is neither a IPv4 address nor a IPv6 address.

class Solution(object):
    def validIPAddress(self, IP):
        """
        :type IP: str
        :rtype: str
        """
        blocks = IP.split('.')
        if len(blocks) == 4:
            for i in xrange(len(blocks)):
                if not blocks[i].isdigit() or not 0 <= int(blocks[i]) < 256 or \
                   (blocks[i][0] == '0' and len(blocks[i]) > 1):
                    return "Neither"
            return "IPv4"

        blocks = IP.split(':')
        if len(blocks) == 8:
            for i in xrange(len(blocks)):
                if not (1 <= len(blocks[i]) <= 4) or \
                   not all(c in string.hexdigits for c in blocks[i]):    
                    return "Neither"
            return "IPv6"
        return "Neither"