Merge branch 'master' of https://github.com/Fizzizist/rosalind-solutions

PERM.pl

@@ -0,0 +1,60 @@
+=pod
+Solution to PERM Rosalind problem
+Generates permutations from 1 to n and totals them
+Author: Peter Vlasveld
+=cut
+
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+
+#Get number from file
+open(IN, "rosalind_perm.txt") or die "Couldn't open the file";
+my $number = <IN>;
+close IN;
+
+#create number array
+my @array = (1..$number); 
+
+#create global variable for return array
+my @finalArr = ();
+
+#open output file for writing
+open(OUT, ">output.txt") or die "Couldn't open output file";
+
+#print result of perm subroutine
+print OUT perm(\@array, 0), "\n";
+
+#print array of permutations
+for (@finalArr){
+	print OUT "@{$_}\n";
+}
+
+#close output file
+close OUT;
+
+#Recursive permutation subroutine
+sub perm{
+	#declare sub variables
+	my ($arr_ref, $num) = @_;
+	my $count = 0;
+	#dereference input array
+	my @arr = @{$arr_ref};
+	
+	#base case - when num = length of array
+	if ($num == $#arr) {
+		push @finalArr, \@arr;
+		return 1;
+	}
+	else 
+	{
+		#perform a swap of num and each other number in the array, and then call the next instance of the sub
+		for ($num..$#arr){
+			($arr[$num], $arr[$_]) = ($arr[$_], $arr[$num]);
+			$count += perm(\@arr, $num+1);
+		}
+		#eventually returns number of permutations
+		return $count;
+	}
+}