The rest of Year 2017

[aoc.git] / 2017 / 49.pl

diff --git a/2017/49.pl b/2017/49.pl
new file mode 100755 (executable)
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--- /dev/null
+++ b/2017/49.pl
@@ -0,0 +1,41 @@
+#!/usr/bin/perl
+
+use v5.30;
+use strict;
+
+my %st_move;
+my %st_write;
+my %st_next;
+my $state;
+my $val;
+my $start_st;
+my $sum_steps;
+while (<>) {
+       if (/Begin in state (\w+)/) {
+               $start_st = $1;
+       } elsif (/Perform a diagnostic checksum after (\d+) steps/) {
+               $sum_steps = $1;
+       } elsif (/In state (\w+):/) {
+               $state = $1;
+       } elsif (/If the current value is (\d):/) {
+               $val = $1;
+       } elsif (/Write the value (\d)./) {
+               $st_write{$state,$val} = $1;
+       } elsif (/Move one slot to the (\w+)/) {
+               $st_move{$state,$val} = $1 eq 'right' ? 1 : -1;
+       } elsif (/Continue with state (\w+)/) {
+               $st_next{$state,$val} = $1;
+       }
+}
+
+my %tape;
+my $pos = 0;
+while ($sum_steps--) {
+       my $val = $tape{$pos} ? 1 : 0;
+       $tape{$pos} = $st_write{$start_st,$val};
+       $pos += $st_move{$start_st,$val};
+       $start_st = $st_next{$start_st,$val};
+}
+
+use List::Util qw(sum);
+say sum values %tape;