#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11161855
use warnings;
use List::AllUtils qw( min_by nsort_by );
$SIG{__WARN__} = sub { die @_ };

my @list1= qw( K B I S Y A Q );
my @list2= qw( B S N A );
my @list3= qw( Y N Q );
my $combined= fancy_algorithm(\@list1, \@list2, \@list3);
use Data::Dump 'dd'; dd 'combined', $combined;

my @lists= (
  [qw( X P Y )],
  [qw( X B Y N )],
  [qw( P B N )],
  [qw( X B P N )],
  [qw( X B P Y )],
  [qw( A Z )],
  [qw( A K L )],
);
$combined= fancy_algorithm(@lists);
use Data::Dump 'dd'; dd 'combined', $combined;

sub fancy_algorithm
  {
  my (%names, @order);
  @names{ @$_ } = () for my @args = @_;
  use Data::Dump 'dd'; dd 'input', \@args;
  while( @args )
    {
    my %names;
    my $see = 1;
    $names{$_} += $see++ for map @$_, @args;
    my @names = nsort_by { $names{$_} } sort +keys %names;
    my %score;
    for ( @args )
      {
      my ($head, @rest) = @$_;
      $score{$head} -= 1e9;
      $score{$_} //= 0 for @rest;
      }
    my $pick = min_by { $score{$_} } @names;
    push @order, $pick;
    $_ = [ grep $pick ne $_, @$_ ] for @args;
    @args = grep @$_, @args;
    }
  return \@order;
  }

[download]

Outputs:

(
  "input",
  [
    ["K", "B", "I", "S", "Y", "A", "Q"],
    ["B", "S", "N", "A"],
    ["Y", "N", "Q"],
  ],
)
("combined", ["K", "B", "I", "S", "Y", "N", "A", "Q"])
(
  "input",
  [
    ["X", "P", "Y"],
    ["X", "B", "Y", "N"],
    ["P", "B", "N"],
    ["X", "B", "P", "N"],
    ["X", "B", "P", "Y"],
    ["A", "Z"],
    ["A", "K", "L"],
  ],
)
("combined", ["X", "B", "P", "Y", "N", "A", "Z", "K", "L"])

[download]

In reply to Re: Merge lists of ordered strings into canonical ordering by tybalt89
in thread Merge lists of ordered strings into canonical ordering by NERDVANA

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