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Q032FreeSystemVerilog

Clean palindrome check

Difficulty
Easy
Topic
Strings
Language
SV
Interview prompt

Question

Return 1 when an ASCII string is a palindrome after ignoring non-alphanumeric bytes and letter case. ASCII letters and digits participate in the comparison.

Candidate starting point

Implementation scaffold

function automatic bit is_alnum(byte c);
  // TODO: identify ASCII letters and digits.
endfunction

function automatic byte to_lower(byte c);
  // TODO: lowercase ASCII uppercase letters; leave other bytes unchanged.
endfunction

function automatic bit is_palindrome_clean(string s);
  // TODO: compare participating bytes from both ends.
endfunction
Reviewed example

Trace one case

Input
s = "A man, a plan, a canal: Panama!"
Expected output
1 (palindrome)

Removing punctuation and folding case produces "amanaplanacanalpanama", which reads the same in both directions.

What to cover

Requirements

  1. Skip non-alphanumeric bytes from both ends.
  2. Compare letters case-insensitively.
  3. Treat an empty cleaned string as a palindrome.
Continue practicing
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