IPv4 Address Validation and Restoration

This problem involves designing and implementing functions to validate and restore IPv4 addresses based on specific rules.

Part A: Validate Dotted IPv4

Write a function isValidIPv4(s) that returns true if s is a valid dotted-decimal IPv4 address and false otherwise.

Requirements for a valid IPv4 address:

• Exactly four decimal octets separated by three dots.
• Each octet must consist of digits only and represent an integer in the range [0, 255].
• No leading zeros are allowed unless the octet itself is exactly "0".
• No plus/minus signs, whitespace, or extra characters are permitted.

Examples:

• "255.255.11.135" -> true
• "-1.255.11.135" -> false
• "01.2.3.4" -> false
• "256.0.0.1" -> false

Part B: Validate Undelimited IPv4 Possibility

Given a string s consisting only of digits (no dots), return true if it can be segmented into a valid IPv4 address by inserting three dots, adhering to the same rules as Part A. Return false otherwise.

Examples:

• "25525511135" -> true (e.g., 255.255.11.135)
• "0002555" -> true (e.g., 0.0.255.55)
• "123" -> false

Part C: Restore All Valid IPv4 Addresses

Given a string s of digits, return all unique valid IPv4 addresses that can be formed by inserting three dots under the rules described in Part A. The addresses can be returned in any order, but duplicates should be excluded.

Example:

• "25525511135" -> ["255.255.11.135", "255.255.111.35"]

Constraints

• For Parts B and C: 1 <= s.length <= 12.
• Aim for an efficient solution, typically involving DFS/backtracking for Parts B and C.