61 lines
1.2 KiB
Perl
61 lines
1.2 KiB
Perl
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=pod
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Solution to PERM Rosalind problem
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Generates permutations from 1 to n and totals them
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Author: Peter Vlasveld
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=cut
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#!/usr/bin/perl
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use strict;
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use warnings;
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#Get number from file
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open(IN, "rosalind_perm.txt") or die "Couldn't open the file";
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my $number = <IN>;
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close IN;
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#create number array
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my @array = (1..$number);
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#create global variable for return array
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my @finalArr = ();
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#open output file for writing
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open(OUT, ">output.txt") or die "Couldn't open output file";
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#print result of perm subroutine
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print OUT perm(\@array, 0), "\n";
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#print array of permutations
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for (@finalArr){
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print OUT "@{$_}\n";
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}
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#close output file
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close OUT;
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#Recursive permutation subroutine
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sub perm{
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#declare sub variables
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my ($arr_ref, $num) = @_;
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my $count = 0;
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#dereference input array
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my @arr = @{$arr_ref};
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#base case - when num = length of array
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if ($num == $#arr) {
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push @finalArr, \@arr;
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return 1;
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}
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else
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{
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#perform a swap of num and each other number in the array, and then call the next instance of the sub
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for ($num..$#arr){
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($arr[$num], $arr[$_]) = ($arr[$_], $arr[$num]);
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$count += perm(\@arr, $num+1);
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}
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#eventually returns number of permutations
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return $count;
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}
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}
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