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All I'm coming up with are trivial methods:

You can just shift each item by n, where @array > n > 1:

my $shift = rand $#array; @array = map { $array[ ($_ + $shift) % @array ]} 0..$#array;

Also, reverse is a derangement for even-sized lists, and for odd-sized lists, I guess you can prepend the middle item and reverse the rest:

my $shift = rand $#array; if (@array % 2 == 0) { @array = map { $array[ ($_ + $shift) % @array} reverse 0..$#array; } else { my $middle = int(@array /2); my @middle = splice @array, $middle, 1; @array = @middle, map { $array[ ($_ + $shift) % @array} reverse 0. +.$#array; };

... but all of these derangements are pretty predictable (that is, from the position of one item, you can infer the positions of all other items with two or three guesses)

In reply to Re: Random Derangement Of An Array by Corion
in thread Random Derangement Of An Array by Limbic~Region

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