Day 18: regexes! and read the task carefully

[aoc2021.git] / 35.pl

diff --git a/35.pl b/35.pl
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+++ b/35.pl
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+#!/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;
+