closed_bracket_word.php

<?php
// 7 kyu - Simple Fun #215: Properly Closed Bracket Word
// We call letter x a counterpart of letter y, if x is the ith letter of the English alphabet, and y is the (27 - i)th for each valid i (1-based). For example, 'z' is the counterpart of 'a' and vice versa, 'y' is the counterpart of 'b', and so on.
//
// A properly closed bracket word (PCBW) is such a word that its first letter is the counterpart of its last letter, its second letter is the counterpart of its last by one letter, and so on.
//
// Determine if the given word is a PCBW or not.
//
// Input/Output
// [input] string word
//
// A string consisting of lowercase letters.
//
// 0 < word.length ≤ 30
//
// [output] a boolean value
//
// true if word is a PCBW, false otherwise.
//
// Example
// For word = "abiryz", the output should be true.
//
// 'a' is the counterpart of 'z';
//
// 'b' <-> 'y'
//
// 'i' <-> 'r'
//
// For word = "aibryz", the output should be false.
//
// For word = "abitryz", the output should be false.

function closed_bracket_word(string $word): bool {
  for($i = 0; $i < strlen($word); $i++) {
    if (ord(strtoupper($word[$i])) - 64 != 27 - (ord(strtoupper($word[strlen($word) -1 - $i])) - 64)) return false;
  }
  return true;
}

// Alternative solutions:
// function closed_bracket_word(string $w): bool {
//   $a = "abcdefghijklmnopqrstuvwxyz";
//   for ($i = 0; $i < strlen($w); $i++) {
//     if (strpos($a, $w[$i]) != 25-strpos($a, $w[strlen($w)-$i-1])) { return false; }
//   }
//   return true;
// }

// function closed_bracket_word(string $word): bool {
//   $al = str_split('abcdefghijklmnopqrstuvwxyz');
//   $total = 1;
//   $word = str_split($word);
//   for($i = 0; $i < count($word)/2; $i++) {
//      if($word[count($word) - ($i + 1)] != $al[25 - array_search($word[$i], $al)]) $total = false;
//   }
//   return $total;
// }

?>