How do you solve Validate IP Address on LeetCode?

Validate IP Address (LeetCode #468) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(1) space complexity. Key insight: Understanding the structure of IP addresses is crucial for validation.

What is the brute force solution for Validate IP Address?

The brute force approach for Validate IP Address is Brute Force, with O(n²) time complexity and O(1) space complexity. The brute-force approach involves checking each character of the input string to determine if it matches the patterns of IPv4 or IPv6 addresses. This method is straightforward but can be inefficient due to multiple checks. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Validate IP Address?

Validate IP Address uses the following concepts: String. The recommended patterns to study are: Regex, String Manipulation.

What are the interview tips for Validate IP Address?

Clearly explain your thought process and the steps you're taking. Consider edge cases, such as empty strings or strings with invalid characters. Practice writing regular expressions, as they can be very useful for string validation problems.

What are common mistakes when solving Validate IP Address?

Not accounting for leading zeros in IPv4 addresses. Misunderstanding the format requirements for IPv6 addresses.

#468

Validate IP Address

Medium

StringRegexString Manipulation

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n)
Space	O(1)	O(1)

💡

Intuition

Time O(n)Space O(1)

The optimal solution uses a single pass to check the format of the IP address, utilizing regular expressions for validation. This reduces the number of checks and improves efficiency.

⚙️

Algorithm

5 steps

1Step 1: Check if the input matches the IPv4 regex pattern.
2Step 2: If it matches, return 'IPv4'.
3Step 3: Check if the input matches the IPv6 regex pattern.
4Step 4: If it matches, return 'IPv6'.
5Step 5: If neither matches, return 'Neither'.

solution.py10 lines

1import re
2
3def validate_ip(queryIP):
4    ipv4_pattern = r'^(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$'
5    ipv6_pattern = r'^([0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}$|^([0-9a-fA-F]{1,4}:){1,7}:$|^::([0-9a-fA-F]{1,4}:){0,6}[0-9a-fA-F]{1,4}$'
6    if re.match(ipv4_pattern, queryIP):
7        return 'IPv4'
8    if re.match(ipv6_pattern, queryIP):
9        return 'IPv6'
10    return 'Neither'

ℹ

Complexity note: The time complexity is O(n) because we only scan the string once to match against the regex patterns. The space complexity is O(1) as we are not using any additional data structures that grow with input size.

1Understanding the structure of IP addresses is crucial for validation.
2Regular expressions can significantly simplify the validation process.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.