#!/usr/bin/perl --
# Simulate the "Monty hall" gameshow problem:
# Suppose you're on a game show, and you're given 
# the choice of three doors: Behind one door is a
# car; behind the others, goats. You pick a door, 
# say No. 1, and the host, who knows what's behind 
# the doors, opens another door, say No. 3, which 
# has a goat. He then says to you, "Do you want to 
# pick door No. 2?" Is it to your advantage to 
# switch your choice?
$swapwins=0;
$noswapwins=0;
$totaltries=1000;
for ($i=0; $i<$totaltries;$i++)
{

	# The price is behind door X.
	$prizedoor=int(rand(3))+1;

	# The door the contestant chooses is random.
	$initialchoice=int(rand(3))+1;

	# The door opened by the gameshow host is not
	# the initial choice, AND is not the prize door.
	do {
		$openedbygameshowhostdoor=int(rand(3))+1;
	} until $openedbygameshowhostdoor!=$initialchoice
	and $openedbygameshowhostdoor!=$prizedoor;

	# Now let's find out which door the contestant
	# would open if he makes the remaining choice
	for ($choice=1;$choice<=3;$choice++)
	{
		if (($choice!=$openedbygameshowhostdoor)
			&& ($choice!=$initialchoice))
		{
			$swapdoor=$choice;
		}
	}

	if ($initialchoice==$prizedoor)
	{
		$noswapwins++;
	} else {
		$noswaplosses++;
	}
	if ($swapdoor==$prizedoor)
	{
		$swapwins++;
	} else {
		$swaplosses++;
	}
	
}
print "Tried playing the game $totaltries times.\n";
print "Swapping rendered $swapwins wins and $swaplosses losses.\n";
print "Not swapping rendered $noswapwins wins and $noswaplosses losses.\n";