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copied!<p>So we have the following:</p> <p>n = length of input word<br/> L = lines in dictionary file</p> <p>If n tends to be small and L tends to be huge, might we be better off finding all permutations of the input word and looking for those, rather than doing something (like sorting) to all L lines of the dictionary file? (Actually, since finding all permutations of a word is O(n!), and we have to run through the entire dictionary file once for each word, maybe not, but I wrote the code anyway.)</p> <p>This is Perl - I know you wanted command-line operations but I don't have a way to do that in shell script that's not super-hacky:</p> <pre><code>sub dedupe { my (@list) = @_; my (@new_list, %seen_entries, $entry); foreach $entry (@list) { if (!(defined($seen_entries{$entry}))) { push(@new_list, $entry); $seen_entries{$entry} = 1; } } return @new_list; } sub find_all_permutations { my ($word) = @_; my (@permutations, $subword, $letter, $rest_of_word, $i); if (length($word) == 1) { push(@permutations, $word); } else { for ($i=0; $i<length($word); $i++) { $letter = substr($word, $i, 1); $rest_of_word = substr($word, 0, $i) . substr($word, $i + 1); foreach $subword (find_all_permutations($rest_of_word)) { push(@permutations, $letter . $subword); } } } return @permutations; } $words_file = '/usr/share/dict/words'; $word = 'table'; @all_permutations = dedupe(find_all_permutations($word)); foreach $permutation (@all_permutations) { if (`grep -c -m 1 ^$permutation\$ $words_file` == 1) { print $permutation . "\n"; } } </code></pre>

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