I would advise to avoid actually removing elements.

Instead have multidimensional hash of column and row.

You can use this multidimensional hash to record

whether a given index has already been supplied before.

Note the use of a closure to make the function stateful.

That is the reason for the reset_hash function.

You must be able to reset the hash for another run.

## just a sketch

my %columns; ## to associate columns with
             ## column numbers
             #
             ## $columns{1} should return
             ## a reference to the
             ## first column list

{ ## closure cleanliness
    my $seen; ## keeps track of what we have seen

    ## used to reset hash within closure between runs
    sub reset_hash{
        undef $seen
    }

    ##function expects column number
    sub find_and_dont_actually_remove_but_say_we_did{
        my $column_number = shift;
        my $column = $columns{$column_number}; ## keeping as a referen
+ce to
                                               ## avoid obscene copy-p
+asta
        my $rand;
        until (not $seen->{$column_number}->{$rand = int(rand(@$column
+))}){
            ## nothing to see here 
        }   
        $seen->{$column_number}->{$rand} = "looks familiar";
        return $column->[$rand]
    }
}

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In reply to Re: Table shuffling challenge by protist
in thread Table shuffling challenge by glow_gene

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