From e28c94a1d8667d492d5a0002b09aea799c7869d3 Mon Sep 17 00:00:00 2001
From: "Jan \"Yenya\" Kasprzak" <kas@fi.muni.cz>
Date: Thu, 24 Nov 2022 16:49:06 +0100
Subject: [PATCH] Mods from 2020

---
 .gitignore   |  4 +--
 2020/13.c    | 47 +++++++++++++++++++++++++++
 2020/46.pl   | 91 ++++++++++++++++++++--------------------------------
 2020/46re.pl | 21 ++++++++++++
 4 files changed, 104 insertions(+), 59 deletions(-)
 create mode 100644 2020/13.c
 create mode 100644 2020/46re.pl

diff --git a/.gitignore b/.gitignore
index 36a44fd..978c3a0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,6 @@
 .*.swp
-*in.txt
-*test.txt
+*.txt
 cache-*.json
 cookie
 id.txt
+a.out
diff --git a/2020/13.c b/2020/13.c
new file mode 100644
index 0000000..a8b92d5
--- /dev/null
+++ b/2020/13.c
@@ -0,0 +1,47 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#define MAXLINE 1000
+#define MAXBAGS 1000
+
+struct bag {
+	char *color;
+	struct baglist *above;
+};
+
+struct baglist {
+	struct bag *bag,
+	struct baglist *next;
+};
+	
+char *bagnames[MAXBAGS];
+
+int main()
+{
+	char buffer[MAXLINE];
+
+	while (fgets(buffer, MAXLINE, stdin)) {
+		char *p;
+		p = strstr(buffer, " bag");
+		*p = 0;
+		printf("bag: %s\n", buffer);
+		p = strstr(p+1, " contain ") + strlen(" contain");
+
+		while (p) {
+			if (*p == ' ')
+				p++;
+			if (*p == 'n') {
+				printf("\tno other\n");
+				break;
+			}
+			int num = atoi(p);
+			char *bag = p = strchr(p, ' ') + 1;
+			p = strstr(p, " bag");
+			*p = 0;
+			p += strlen(" bag");
+			printf("\t%d, %s.\n", num, bag);
+			p = strchr(p, ' ');
+		}
+	}
+}
diff --git a/2020/46.pl b/2020/46.pl
index b9744b8..360edb7 100755
--- a/2020/46.pl
+++ b/2020/46.pl
@@ -2,74 +2,51 @@
 
 use strict;
 
-my $rounds;
-($rounds, $_) = @ARGV;
-
-my @cups_nums = split //;
-my @cups_pos;
-my $i;
-for (@cups_nums) {
-	$cups_pos[$_] = $i++;
-}
-
-my $max = 1_000_000;
-
-my ($prev, @cups, $one);
-for (@cups_nums, 10 .. $max) {
-	my $cup = {
-		num => $_,
-		prev_num => $prev,
-		next => undef,
-	};
-	push @cups, $cup;
-	$one = $cup if $cup->{num} == 1;
+my ($rounds, $max, $cups) = @ARGV;
+
+my @next_cup = (1 .. $max);
+my $i = 0;
+my $prev = @next_cup - 1;
+my $cur;
+for my $cup (split //, $cups) {
+	$cup--; # count cup numbers from 0, not from 1
+	$next_cup[$prev] = $cup;
 	$prev = $cup;
+	$cur //= $cup; # The first one
 }
-
-$prev = $cups[-1];
-for my $cup (@cups) {
-	$cup->{prev_num} = $cups[$cups_pos[$cup->{num}-1]]
-		if $cup->{num} > 1 && $cup->{num} <= 10;
-	$cup->{prev_num} = $cups[-1]
-		if $cup->{num} == 1;
-	$prev->{next} = $cup;
-	$prev = $cup;
-}
-
-# for my $cup (@cups) {
-# 	print $cup->{num}, ": >", $cup->{next}->{num}, " <", $cup->{prev_num}->{num}, "\n";
-# }
-
-my $cur = $cups[0];
+# $next_cup[6] = 2;
 
 while ($rounds--) {
 	my @pickup;
-	my $cup = $cur->{next};
-	my $dest = $cur->{prev_num};
-	my %num_seen;
+	my $cup = $next_cup[$cur];
+	my %num_seen = ($cur => 1);
 	# print "pickup: ";
 	for (1..3) {
 		push @pickup, $cup;
-		$num_seen{ $cup->{num} } = 1;
-		# print $cup->{num}, ' ';
-		$cup = $cup->{next};
+		$num_seen{ $cup } = 1;
+		# print $cup + 1, ' ';
+		$cup = $next_cup[$cup];
 	}
-	$dest = $dest->{prev_num} while $num_seen{$dest->{num}};
-	# print " dest: ", $dest->{num}, "\n";
-	$cur->{next} = $cup;
-	my $end = $dest->{next};
-	$dest->{next} = $pickup[0];
-	$pickup[-1]->{next} = $end;
-
-	$cur = $cur->{next};
-	# $end = $cur;
+	my $dest = $cur;
+	while ($num_seen{$dest}) {
+		$dest--;
+		$dest = $max-1 if $dest < 0;
+	}
+	# print " dest: ", $dest + 1, "\n";
+	$next_cup[$cur] = $cup;
+	my $end = $next_cup[$dest];
+	$next_cup[$dest] = $pickup[0];
+	$next_cup[$pickup[-1]] = $end;
+
+	$cur = $next_cup[$cur];
+	$end = $cur;
 	# do {
-	# 	print $end->{num}, ',';
-	# 	$end = $end->{next};
-	# } while ($end->{num} != $cur->{num});
+	#  	print $end+1, ',';
+	# 	$end = $next_cup[$end];
+	# } while ($end != $cur);
 	# print "\n";
 	print "round $rounds\n" if $rounds % 100_000 == 0;
 }
 
-print "one -> ", $one->{next}->{num}, '*', $one->{next}->{next}->{num},
-	"=", $one->{next}->{num} * $one->{next}->{next}->{num}, "\n";
+print "one -> ", $next_cup[0] + 1, '*', $next_cup[$next_cup[0]] + 1,
+	"=", ($next_cup[0]+1) * ($next_cup[$next_cup[0]]+1), "\n";
diff --git a/2020/46re.pl b/2020/46re.pl
new file mode 100644
index 0000000..442b5ff
--- /dev/null
+++ b/2020/46re.pl
@@ -0,0 +1,21 @@
+#!/usr/bin/perl -w
+
+use strict;
+
+my $rounds;
+($rounds, $_) = @ARGV;
+$_ .= '3' x 10_000_000;
+
+while ($rounds--) {
+	my ($cur) = /\A(.)/;
+	do {
+		$cur--;
+		$cur = 9 if $cur == 0;
+	} while (/\A.{1,3}$cur/);
+	
+	s/\A(.)(...)(.*)$cur(.*)\z/$3$cur$2$4$1/;
+	# print $_, "\n";
+}
+
+s/\A(.*)1(.*)\z/Result is $2$1\n/;
+print;
-- 
2.43.5