From 756f22d58bb198b8f34589c112e1003614ccdcd6 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Sun, 2 Nov 2025 21:41:58 +0100
Subject: aoc 2017, days 1-20

---
 2017/src/day11.cpp | 104 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 104 insertions(+)
 create mode 100644 2017/src/day11.cpp

(limited to '2017/src/day11.cpp')

diff --git a/2017/src/day11.cpp b/2017/src/day11.cpp
new file mode 100644
index 0000000..ea945c1
--- /dev/null
+++ b/2017/src/day11.cpp
@@ -0,0 +1,104 @@
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <sstream>
+#include <string>
+#include <vector>
+
+// see: https://www.redblobgames.com/grids/hexagons/
+
+using namespace std;
+
+namespace {
+
+string
+read_file(const filesystem::path& filename)
+{
+	ifstream file{ filename };
+	string   line;
+	getline(file, line);
+	return line;
+}
+
+vector<string>
+split(const string& line)
+{
+	stringstream   strm{ line };
+	vector<string> data;
+
+	for ( string word; getline(strm, word, ','); ) {
+		data.emplace_back(word);
+	}
+
+	return data;
+}
+
+void
+part1(const vector<string>& steps)
+{
+	// string => (q, s, r)
+	map<string, tuple<int, int, int>> dirs{
+		{ "n", { 0, 1, -1 } },
+		{ "nw", { -1, 1, 0 } },
+		{ "sw", { -1, 0, 1 } },
+		{ "s", { 0, -1, 1 } },
+		{ "se", { 1, -1, 0 } },
+		{ "ne", { 1, 0, -1 } }
+	};
+
+	tuple<int, int, int> current = { 0, 0, 0 };
+	for ( const auto& step: steps ) {
+		const auto [dq, ds, dr] = dirs.at(step);
+
+		get<0>(current) += dq;
+		get<1>(current) += ds;
+		get<2>(current) += dr;
+	}
+
+	auto dist = (abs(get<0>(current)) + abs(get<1>(current)) + abs(get<2>(current))) / 2;
+
+	cout << "Part1: " << dist << '\n';
+}
+
+void
+part2(const vector<string>& steps)
+{
+	// string => (q, s, r)
+	map<string, tuple<int, int, int>> dirs{
+		{ "n", { 0, 1, -1 } },
+		{ "nw", { -1, 1, 0 } },
+		{ "sw", { -1, 0, 1 } },
+		{ "s", { 0, -1, 1 } },
+		{ "se", { 1, -1, 0 } },
+		{ "ne", { 1, 0, -1 } }
+	};
+
+	int max_dist = 0;
+
+	tuple<int, int, int> current = { 0, 0, 0 };
+	for ( const auto& step: steps ) {
+		const auto [dq, ds, dr] = dirs.at(step);
+
+		get<0>(current) += dq;
+		get<1>(current) += ds;
+		get<2>(current) += dr;
+
+		auto dist = (abs(get<0>(current)) + abs(get<1>(current)) + abs(get<2>(current))) / 2;
+
+		max_dist = max(max_dist, dist);
+	}
+
+	cout << "Part2: " << max_dist << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+	auto line  = read_file("data/day11.txt");
+	auto steps = split(line);
+	part1(steps);
+	part2(steps);
+}
-- 
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