rectangle-ball.pl

#!/usr/bin/env perl
use strict;
use warnings;


my $max_height = shift;
my $max_width = shift;



# 0 ------------- +
#  |
#  |
#  |
#  |
#  |
#  |
#  + 

my $status = {
      width  => 0,
      height => 0,
      dx     => 1, #右
      dy     => 1,#下
};

my $counter = 1;

while (1) {
    my $new_status = next_status($status);

    print "$counter ($new_status->{height}, $new_status->{width})\n";

    if (is_goal($new_status->{height}, $new_status->{width}) && $counter != 1)  {
      print "GOAL!\n";
      exit 0;
    }

    $status = $new_status;
    $counter++;
}

sub is_goal {
  my ($height, $width) = @_;

  if (($width == 1 ) || $width == $max_width) {
    return 1 if ($height == 1); #左右の上の角
    return 1 if ($height == $max_height); #左右の下の角
  }

  return 0;
}


sub next_status {
  my $status = shift;

  my ($new_height, $new_dy) = new_coordinate($status->{height}, $status->{dy}, $max_height);
  my ($new_width, $new_dx) = new_coordinate($status->{width}, $status->{dx}, $max_width);

  my $new_status =  {
      width  => $new_width,
      height => $new_height,
      dx     => $new_dx,
      dy     => $new_dy,
  };

  return $new_status;
}


sub new_coordinate {
  my ($coordinate, $d, $max_coordinate) = @_;

  my $new_coordinate = $coordinate + $d;
  my $new_d = $d;

  if ($new_coordinate < 1 ) { #上もしくは左の壁
        $new_coordinate += 2; #-1が来ているので2を足して1にする
        $new_d *= -1;
  }

  if ($new_coordinate > $max_coordinate) { #下もしくは右の壁
        $new_coordinate -= 2; 
        $new_d *= -1; 
  }

  return $new_coordinate, $new_d;
}