aoc2021

commit 2247d9305702f1804f846070d00a05aa3e2a1fa1
parent 71b0c0e84554c0a236fbb9fe3547774452bb2f5a
Author: Samir Parikh <noreply@samirparikh.com>
Date:   Mon,  6 Dec 2021 20:21:40 +0000

add day04-2.pl

Diffstat:
A
day04-2.pl
 | 
172
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 172 insertions(+), 0 deletions(-)
diff --git a/day04-2.pl b/day04-2.pl
@@ -0,0 +1,172 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use v5.22;
+
+sub get_filehandle {
+    if (@ARGV !=1) {
+        die "Usage: $0 [input-filename]";
+    }
+    my $input_filename = $ARGV[0];
+    open my $filehandle, '<', $input_filename or
+        die "Could not open input file $input_filename: $!";
+    return $filehandle;
+}
+
+sub get_numbers {
+    my $fh = shift;
+    chomp( my $numbers = ( <$fh> ) );
+    return (split( ",", $numbers));
+}
+
+sub initialize_boards {
+    my $fh = shift;
+    chomp( my @input = ( <$fh> ) );
+    my (@boards, @new_board);
+    foreach (@input) {
+        if (/\A\s*\Z/) {
+            push(@boards, [@new_board]) if (@new_board);
+            @new_board = ();
+        } else {
+            push(@new_board, [split]);
+        }
+    }
+    push(@boards, \@new_board);
+    return (@boards);
+}
+
+sub initialize_state {
+    my %state;
+    my $boards = shift;
+    foreach my $board (@$boards) {
+        foreach my $row (@$board) {
+            foreach my $column (@$row) {
+                $state{$board}{$row}{$column} = 0;
+            }
+        }
+    }
+    return %state;
+}
+
+sub play_turn {
+    my ($number, $boards, $state) = @_;
+    foreach my $board (@$boards) {       # $board is ref to board array
+        foreach my $row (@$board) {      # $row is ref to board row array
+            foreach my $column (@$row) { # $column is element of row array
+                if ($column == $number) {
+                    $state->{$board}{$row}{$column} = 1;
+                }
+            }
+        }
+    }
+}
+
+# for debugging purposes only
+sub print_board_state {
+    my ($boards, $state) = @_;
+    foreach my $board (@$boards) {       # $board is ref to board array
+        foreach my $row (@$board) {      # $row is ref to board row array
+            foreach my $column (@$row) { # $column is element of row array
+                print "$board\t$row\t";
+                if ($state->{$board}{$row}{$column} == 1) {
+                    printf "-> %2d <-\n", $column;
+                } else {
+                    printf "   %2d\n", $column;
+                }
+            }
+        }
+    }
+}
+
+sub check_for_winner {
+    my ($boards, $state) = @_;
+    my @winning_board_ref;
+# check for row wins
+    foreach my $board (@$boards) {       # $board is ref to board array
+        foreach my $row (@$board) {      # $row is ref to board row array
+            my $total = 0;
+            foreach my $column (@$row) { # $column is the actual value of
+                                         # the number in @$row
+                $total += $state->{$board}{$row}{$column};
+            }
+            if ($total == 5) {
+                #say "found row winner";
+                push (@winning_board_ref, $board);
+                #return $board;
+                last;
+            }
+        }
+# for each board, iterate through each column (0 .. 4)
+        foreach (0 .. 4) {
+            my $total = 0;
+            foreach my $row (@$board) {
+# here, $_ represents the index within the array @$row.  Because the hash key
+# stores the actual value, we need to deference $row (which is an array
+# reference) and then look up the value stored in the index $_
+                $total += $state->{$board}{$row}{$row->[$_]};
+            }
+            if ($total == 5) {
+                #say "found column winner";
+                push (@winning_board_ref, $board);
+                #return $board;
+                last;
+            }
+        }
+    }
+    return @winning_board_ref;
+}
+
+sub calculate_score {
+    my ($number, $board, $state) = @_;
+    my $score = 0;
+    foreach my $row (@$board) {     # $row is ref to board row array
+        foreach my $column (@$row) { # $column is element of row array
+            if ($state->{$board}{$row}{$column} == 0) {
+                $score += $column;
+            }
+        }
+    }
+    return $score *= $number;
+}
+
+# Advent of Code 2021 Day 04 Part 1
+# initialize game variables
+my $filehandle  = get_filehandle();
+my @numbers     = get_numbers($filehandle);
+my $number;
+my @boards      = initialize_boards($filehandle);
+my %state       = initialize_state(\@boards);
+my $turn = 0;
+
+# $winner_found plays double duty.  When equal to 0, it means that
+# we haven't yet found a winning board.  When we do, the subroutine
+# check_for_winner returns a reference to the array of the winning
+# board which we can then submit to calculate_score.
+#my $winner_found = 0;
+my @winner_found;
+
+#until ($winner_found) {
+while ( scalar ( @boards ) > 1 ) {
+    @winner_found = ();
+    $turn++;
+    printf "turn: %2d, playing number %2d\n", $turn, $number;
+    $number = shift( @numbers );
+    play_turn($number, \@boards, \%state);
+    $winner_found = check_for_winner(\@boards, \%state);
+    if ( @winner_found ) {
+        say "found a winning board";
+        say "we had ", scalar(@boards), " boards";
+        foreach my $winning_board (@winner_found) {
+            @boards = grep { $_ ne $winning_board } @boards;
+        }
+        say "we now have ", scalar(@boards), " boards";
+    }
+    unless (@numbers) { # if we run out of numbers
+        say "Out of numbers.  No winner found.";
+        #last;
+        exit;
+    }
+}
+my $score = calculate_score($number, $boards[0], %state);
+say "winning score is $score";