(Image courtesy Tomohiro Tachi under Creative Commons license.)
Recently I came across a fun programming challenge called the Pythagoras Pie, which was described as:
At a party a pie is to be shared by 100 guests. The first guest gets 1% of the pie, the second guest gets 2% of the remaining pie, the third gets 3% of the remaining pie, the fourth gets 4% and so on.
Write a script that figures out which guest gets the largest piece of pie.
I sat down for a few minutes, and wrote the obvious code. It iterates over the list of guests. For each guest, it calculates how large a piece of pie the guest will get. All the while, it stores size of the largest piece of pie it has seen so far.
Here is a solution in Perl.
sub slice_pie {
my $iters = shift;
my $pie = 1;
my $largest = 0;
my $winner = 0;
for ( 0 .. $iters ) {
my $iter_value = $_ * .01;
my $portion = ( $iter_value * $pie );
$pie = $pie - $portion;
if ( $portion >= $largest ) {
$largest = $portion;
$winner = $_;
}
}
print qq[Winner is guest # $winner with the largest portion: $largest\n];
}
slice_pie(100);
The answer, as it turns out, is that the 10th guest gets the largest piece of the pie: 0.0628156509555295, or about 6%.
Just for fun, I wrote almost the same exact code once again, except this time in Perl 6. Even though this is a straightforward translation using the same basic loop structure, it has a few nice improvements:
- No need for argument unpacking (saves a horizontal line — vertical compactness is good)
- Nice type annotations mean we can call an integer an
Int, which also helps the compiler - No need for parens around the
forandifchecks
sub slice-pie(Int $iters) {
my $pie = 1;
my $largest = 0;
my Int $winner;
for 0 .. $iters {
my $iter_value = $_ * .01;
my $portion = $iter_value * $pie;
$pie -= $portion;
if $portion >= $largest {
$largest = $portion;
$winner = $_;
}
}
say qq[Winner is guest number $winner with the largest portion: $largest ];
}
slice-pie(100);
