dictionary_solution.php

/**
 * Solution to the following:
 * Given a dictionary, output all word pairs where both words share all their letters except the last two, which are distinct and reversed.
 * 
 * Notes:
 *   - Use a reasonable dictionary of your choice
 *   - Potential word pairs are: "ear, era" ; "revies, revise" ; "burglaries, burglarise"
 *   - "shear, era" is not a valid pair because "she" != "e"
 *   - "bell, bell" is not a valid pair because the last two letters are not distinct
 *   - This will be benchmarked
 *   - Work on this problem in C, C++, Java, Perl, PHP, Python or a similar language.
 *   - Don't e-mail to ask for clarifications on this question.
 *     Make reasonable assumptions and justify them in a README if you feel the need
 */

<?php
$time = microtime();
$results = array();
$dictionary = array();

// copy the contents of the file to our dictionary
$file = fopen("dictionary.txt", "r");
if ($file) {
    while (!feof($file)) {
        $dictionary[] = trim(fgets($file));
    }
    fclose($file);
}

$dictionary = array_unique($dictionary);

// compile our word pairs from the dictionary
while ($curr = array_shift($dictionary)) {
    $length = strlen($curr);
    if ($length < 2 || $curr[$length-1] == $curr[$length-2])
        continue;
    $search = substr($curr, 0, $length-2) . $curr[$length-1] . $curr[$length-2];
    $result = array_search($search, $dictionary);
    if ($result !== FALSE) {
        $results[] = $curr . ", " . $dictionary[$result];
        unset($dictionary[$result]);
    }
}
$time = microtime() - $time;
echo "<p>" . implode($results, '<br>') . "</p>";
echo "<p>Found " . count($results) . " pairs in " . ($time) . " seconds</p>";
?>