Day 18: regexes! and read the task carefully

diff --git a/35.pl b/35.pl
new file mode 100755 (executable)
index 0000000..53e1e3e
--- /dev/null
+++ b/35.pl
@@ -0,0 +1,46 @@
+#!/usr/bin/perl -w
+
+use v5.16;
+
+chomp (my $res = <>);
+while (<>) {
+       chomp;
+       say "\nadd:   $res\nto:    $_";
+       $res = "[$res,$_]";
+       ACTION:
+       while (1) {
+               say "have:  $res";
+               # explode
+               my $depth = 0;
+               for my $i (0 .. length($res)-1) {
+                       $depth++ if substr($res, $i, 1) eq '[';
+                       $depth-- if substr($res, $i, 1) eq ']';
+                       
+                       if ($depth >= 5) {
+                               pos($res) = $i;
+                               next if $res !~ /\G\[(\d+),(\d+)\]/;
+                               say "explode at $i";
+                               pos($res) = $i;
+                               $res =~ s/\G\[(\d+),(\d+)\]/X/;
+                               say "X:     $res";
+                               my $l = $1;
+                               my $r = $2;
+                               $res =~ s/(\d+)([^\d]*X)/($1+$l).$2/e;
+                               $res =~ s/(X[^\d]*)(\d+)/"$1".($2+$r)/e;
+                               $res =~ s/X/0/;
+                               say "after: $res";
+                               next ACTION;
+                       }
+               }
+               # split
+               if ($res =~ s|\d{2,}|'['.int($&/2).','.int(($&+1)/2).']'|e) {
+                       say "split: $res";
+                       next ACTION;
+               }
+               last;
+       }
+}
+
+1 while $res =~ s/\[(\d+),(\d+)\]/3*$1+2*$2/e;
+say $res;
+

diff --git a/36.pl b/36.pl
new file mode 100755 (executable)
index 0000000..4371f37
--- /dev/null
+++ b/36.pl
@@ -0,0 +1,58 @@
+#!/usr/bin/perl -w
+
+use v5.16;
+
+$/ = undef;
+my @nums = split /\n/, <>;
+
+my $max = 0;
+for my $i (0 .. $#nums) {
+for my $j (0 .. $#nums) {
+       next if $i == $j;
+       my $r = add($nums[$i], $nums[$j]);
+       $max = $r if ($max < $r);
+} }
+
+say $max;
+
+sub add {
+       my ($n1, $n2) = @_;
+       say "\nadd:   $n1\nto:    $n2";
+       my $res = "[$n1,$n2]";
+       ACTION:
+       while (1) {
+               say "have:  $res";
+               # explode
+               my $depth = 0;
+               for my $i (0 .. length($res)-1) {
+                       $depth++ if substr($res, $i, 1) eq '[';
+                       $depth-- if substr($res, $i, 1) eq ']';
+                       
+                       if ($depth >= 5) {
+                               pos($res) = $i;
+                               next if $res !~ /\G\[(\d+),(\d+)\]/;
+                               say "explode at $i";
+                               pos($res) = $i;
+                               $res =~ s/\G\[(\d+),(\d+)\]/X/;
+                               say "X:     $res";
+                               my $l = $1;
+                               my $r = $2;
+                               $res =~ s/(\d+)([^\d]*X)/($1+$l).$2/e;
+                               $res =~ s/(X[^\d]*)(\d+)/"$1".($2+$r)/e;
+                               $res =~ s/X/0/;
+                               say "after: $res";
+                               next ACTION;
+                       }
+               }
+               # split
+               if ($res =~ s|\d{2,}|'['.int($&/2).','.int(($&+1)/2).']'|e) {
+                       say "split: $res";
+                       next ACTION;
+               }
+               last;
+       }
+       1 while $res =~ s/\[(\d+),(\d+)\]/3*$1+2*$2/e;
+       return $res;
+}
+
+