From bdd35a7bee7f23c912d0c453abc263805d8d8ccf Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Fri, 7 Nov 2025 12:04:46 +0100
Subject: aoc 2017, days 21-25

---
 2017/src/day24.cpp | 102 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)
 create mode 100644 2017/src/day24.cpp

(limited to '2017/src/day24.cpp')

diff --git a/2017/src/day24.cpp b/2017/src/day24.cpp
new file mode 100644
index 0000000..fa4148c
--- /dev/null
+++ b/2017/src/day24.cpp
@@ -0,0 +1,102 @@
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <set>
+#include <vector>
+
+using namespace std;
+
+namespace {
+
+vector<tuple<long, long>>
+read_file(const filesystem::path& filename)
+{
+	ifstream                  file{ filename };
+	vector<tuple<long, long>> data;
+
+	long lhs = 0;
+	long rhs = 0;
+	char sep = 0;
+
+	while ( file >> lhs >> sep >> rhs ) {
+		data.emplace_back(lhs, rhs);
+	}
+	return data;
+}
+
+long
+strongest(const vector<tuple<long, long>>& data, long current = 0, const set<size_t>& used = {})
+{
+	long best_strength = 0;
+
+	for ( size_t i = 0; i != data.size(); ++i ) {
+		if ( used.contains(i) ) {
+			continue;
+		}
+
+		auto [lhs, rhs] = data.at(i);
+		if ( lhs == current || rhs == current ) {
+			auto next_port = (lhs == current) ? rhs : lhs;
+			auto new_used{ used };
+			new_used.emplace(i);
+			auto strength = lhs + rhs + strongest(data, next_port, new_used);
+			best_strength = max(best_strength, strength);
+		}
+	}
+
+	return best_strength;
+}
+
+tuple<long, size_t>
+strongest_and_longest(const vector<tuple<long, long>>& data, long current = 0, const set<size_t>& used = {})
+{
+	long   best_strength = 0;
+	size_t best_length   = 0;
+
+	for ( size_t i = 0; i != data.size(); ++i ) {
+		if ( used.contains(i) ) {
+			continue;
+		}
+
+		auto [lhs, rhs] = data.at(i);
+		if ( lhs == current || rhs == current ) {
+			auto next_port = (lhs == current) ? rhs : lhs;
+			auto new_used{ used };
+			new_used.emplace(i);
+			auto [sub_strength, sub_length] = strongest_and_longest(data, next_port, new_used);
+
+			auto total_strength = sub_strength + lhs + rhs;
+			auto total_length   = sub_length + 1;
+
+			if ( total_length > best_length || (total_length == best_length && total_strength > best_strength) ) {
+				best_strength = total_strength;
+				best_length   = total_length;
+			}
+		}
+	}
+
+	return make_tuple(best_strength, best_length);
+}
+
+void
+part1(const vector<tuple<long, long>>& data)
+{
+	cout << "Part1: " << strongest(data) << '\n';
+}
+
+void
+part2(const vector<tuple<long, long>>& data)
+{
+	auto [strength, length] = strongest_and_longest(data);
+	cout << "Part2: " << strength << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+	auto data = read_file("data/day24.txt");
+	part1(data);
+	part2(data);
+}
-- 
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