From e182df9e4daf4968750f1414853f4aa1a1e94b15 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Sat, 9 Dec 2023 09:08:34 +0100
Subject: Lösung für Tag 8
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---
 src/day08.cpp | 110 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 src/day08.cpp

(limited to 'src')

diff --git a/src/day08.cpp b/src/day08.cpp
new file mode 100644
index 0000000..3e1b6c9
--- /dev/null
+++ b/src/day08.cpp
@@ -0,0 +1,110 @@
+#include <array>
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <regex>
+#include <numeric>
+using namespace std;
+
+struct Generator {
+	explicit Generator(string_view init)
+	    : values_(init)
+	    , iter_(values_.begin())
+
+	{
+	}
+
+	size_t next()
+	{
+		size_t gen = (*iter_ == 'L') ? 0 : 1;
+
+		++iter_;
+		if ( iter_ == values_.end() ) {
+			iter_ = values_.begin();
+		}
+
+		return gen;
+	}
+
+	string           values_;
+	string::iterator iter_;
+};
+
+void
+part1()
+{
+	fstream input{ "data/day08.txt" };
+
+	string line;
+	getline(input, line);
+
+	Generator generator{ line };
+
+	map<string, array<string, 2>> puzzle;
+
+	const regex pattern{ R"((.*) = \((.*), (.*)\))" };
+	while ( getline(input, line) ) {
+		if ( line.empty() ) {
+			continue;
+		}
+
+		smatch sub_match;
+		if ( regex_search(line, sub_match, pattern) ) {
+			puzzle[sub_match[1]] = { sub_match[2], sub_match[3] };
+		}
+	}
+
+	auto counter = 0;
+	for ( string str{ "AAA" }; str != "ZZZ"; str = puzzle[str][generator.next()] ) {
+		++counter;
+	}
+	cout << counter << endl;
+}
+
+void
+part2()
+{
+	fstream input{ "data/day08.txt" };
+
+	string firstline;
+	getline(input, firstline);
+
+	map<string, array<string, 2>> puzzle;
+
+	const regex pattern{ R"((.*) = \((.*), (.*)\))" };
+	for ( string line; getline(input, line); ) {
+		if ( line.empty() ) {
+			continue;
+		}
+
+		smatch sub_match;
+		if ( regex_search(line, sub_match, pattern) ) {
+			puzzle[sub_match[1]] = { sub_match[2], sub_match[3] };
+		}
+	}
+
+	auto value = 1L;
+	for ( const auto& entry: puzzle ) {
+		if ( entry.first[2] != 'A' ) {
+			continue;
+		}
+
+		Generator generator{ firstline };
+
+		auto counter = 0L;
+
+		for ( string str{ entry.first }; str[2] != 'Z'; str = puzzle[str][generator.next()] ) {
+			++counter;
+		}
+
+		value = lcm(value, counter);
+	}
+	cout << value << endl;
+}
+
+int
+main()
+{
+	part1();
+	part2();
+}
-- 
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