dHondt

#!/usr/bin/perl -W
# Calculate seats in parliament according d'Hondt's method
# Elmar Klausmeier, 22-Feb-2014

use strict;
use Getopt::Std;
my %opts = ('d' => 0, 's' => 2);
getopts('ds:',\%opts);
my $s = (($opts{'s'} > 0) ? $opts{'s'} : 2);

my (@F,@votes,@party,@seat,@calc,@divisor,$i,$j,$n,$max,$multi,@drawing);

while (<>) {
	@F = split;
	push @party,$F[0];
	push @votes,$F[1];
	push @calc,$F[1];
}

print "Number of seats: $s\n";
$n = $#votes;
for ($i=0; $i<=$n; ++$i) {
	print "\t$party[$i] - $votes[$i]\n";
}

# @votes does not need to be sorted in any way
for ($i=0; $i<=$n; ++$i) {
	($seat[$i],$divisor[$i]) = (0,1);
}

# $u is used seats so far
for (my $u=0; $u<$s; ++$u) {
	($max,$j) = ($calc[0],0);	# calculate maximum in @calc
	$drawing[$multi=0] = 0;
	for ($i=1; $i<=$n; ++$i) {
		if ($calc[$i] > $max) {
			($max,$j) = ($calc[$i],$i);
			$drawing[$multi=0] = $i;
		} elsif ($calc[$i] == $max) {
			$drawing[++$multi] = $i;
		}
	}
	#print "multi=$multi\n";
	if ($u + $multi >= $s) {
		printf("Drawing of lots for %d seats required for parties:", $s - $u);
		for ($i=0; $i<=$multi; ++$i) {
			print " $party[$drawing[$i]]";
		}
		print "\n";
		last;
	}
	$seat[$j] += 1;
	$divisor[$j] += 1;	# this is specific for d'Hondt
	$calc[$j] = int($votes[$j] / $divisor[$j]);
}

for ($i=0; $i<=$n; ++$i) {
	print "$party[$i] - $seat[$i]\n";
}