Convert a Hexadecimal Address to Dotted IPv4
Company: Microsoft
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Onsite
Convert a 32-bit hexadecimal address to dotted-decimal IPv4 notation.
Implement `hex_to_ipv4(text: string) -> string`.
### Constraints & Assumptions
The source reports a hex-to-IPv4 conversion without exact formatting rules. This practice contract uses network-order bytes: the leftmost byte is the first decimal octet.
- Input length is at most 100. Accept exactly eight hexadecimal digits, optionally preceded by `0x` or `0X`.
- Hexadecimal digits are case-insensitive. Whitespace, signs, separators, and any other length or character are invalid.
- On valid input return four decimal octets separated by dots, without leading zeroes. On invalid input return `INVALID`.
- Treat the value as an unsigned 32-bit bit pattern; addresses whose high bit is set are valid.
### Examples
```text
hex_to_ipv4("C0A80101") -> "192.168.1.1"
hex_to_ipv4("0xffffffff") -> "255.255.255.255"
hex_to_ipv4("00000000") -> "0.0.0.0"
hex_to_ipv4("1FF") -> "INVALID"
```
Explain how your byte-order choice and signed-integer handling affect the result. A solution that parses four two-character byte values can avoid signed 32-bit overflow entirely.
Overview: Convert an eight-digit hexadecimal address to network-order dotted IPv4 with strict validation, optional prefixes, and correct high-bit handling.
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Convert a 32-bit hexadecimal address to dotted-decimal IPv4 notation.
Implement `hex_to_ipv4(text: string) -> string`.
### Constraints & Assumptions
The source reports a hex-to-IPv4 conversion without exact formatting rules. This practice contract uses network-order bytes: the leftmost byte is the first decimal octet.
- Input length is at most 100. Accept exactly eight hexadecimal digits, optionally preceded by `0x` or `0X`.
- Hexadecimal digits are case-insensitive. Whitespace, signs, separators, and any other length or character are invalid.
- On valid input return four decimal octets separated by dots, without leading zeroes. On invalid input return `INVALID`.
- Treat the value as an unsigned 32-bit bit pattern; addresses whose high bit is set are valid.
### Examples
```text
hex_to_ipv4("C0A80101") -> "192.168.1.1"
hex_to_ipv4("0xffffffff") -> "255.255.255.255"
hex_to_ipv4("00000000") -> "0.0.0.0"
hex_to_ipv4("1FF") -> "INVALID"
```
Explain how your byte-order choice and signed-integer handling affect the result. A solution that parses four two-character byte values can avoid signed 32-bit overflow entirely.
Constraints
- Input is a string of length at most 100.
- Accept exactly eight ASCII hexadecimal digits, optionally preceded by 0x or 0X; digits are case-insensitive.
- Whitespace, signs, separators and any other length or character return INVALID.
- Use network-order bytes, including unsigned 32-bit patterns with the high bit set.
- Valid output has four decimal octets separated by dots, without leading zeroes.
Examples
Input: ('C0A80101',)
Expected Output: '192.168.1.1'
Explanation: Network order keeps the leftmost byte first.
Input: ('0xffffffff',)
Expected Output: '255.255.255.255'
Explanation: An unsigned high-bit value is valid.