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How can I print all the numbers from 1 to n in random order?

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Contributed by vroom on Jan 17, 2000 at 09:16 UTC
Q&A  > numbers


Answer: How can I print all the numbers from 1 to n in random order?
contributed by ChrisS

I'd use the List::Util module.

use List::Util qw(shuffle); my $n = 10; # use $ARGV[0] or whatever to set $n print join " ", shuffle(1 .. $n);
Answer: How can I print all the numbers from 1 to n in random order?
contributed by btrott

I don't see the original here, so I don't know if this has been suggested... but you could just stick the numbers in an array, then shuffle the array, then print them. Use the Fisher-Yates Shuffle, which avoids the splice quadratic algorithm bit.

sub fisher_yates_shuffle { my $array = shift; my $i; for ($i = @$array; --$i; ) { my $j = int rand ($i+1); next if $i == $j; @$array[$i,$j] = @$array[$j,$i]; } } my $N = 50; my @array = (1..$N); fisher_yates_shuffle( \@array ); # permutes @array in place print "@array";
From perlfaq4, How do I shuffle an array randomly?.
Answer: How can I print all the numbers from 1 to n in random order?
contributed by lanval

$ cat numbers.pl

#!/usr/bin/perl sub RandomiseArray { my (%b, $c); map { do { $c = rand } until(!exists $b{$c}); $b{$c} = $_ } @_ +; return values(%b); } my @a = RandomiseArray(1..10); print "@a\n";
$ ./numbers.pl
8 5 1 3 10 2 6 4 9 7
$ ./numbers.pl
4 2 3 9 5 8 6 1 7 10
$ ./numbers.pl
8 10 7 6 5 9 2 3 4 1


Yeah?
Answer: How can I print all the numbers from 1 to n in random order?
contributed by chromatic

Hmm, see splice for why that doesn't work. Here's the fix: print (splice @a, rand @a, 1);

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