From d89b7d7fcf5a42bc5a7e0eef1304c73a09929611 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Tue, 9 Dec 2025 08:50:50 +0100
Subject: aoc 2025, day 9, part 1

---
 2025/src/day09.cpp | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 2025/src/day09.cpp

(limited to '2025/src')

diff --git a/2025/src/day09.cpp b/2025/src/day09.cpp
new file mode 100644
index 0000000..f46112a
--- /dev/null
+++ b/2025/src/day09.cpp
@@ -0,0 +1,56 @@
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <tuple>
+#include <vector>
+
+using namespace std;
+
+namespace {
+
+using Pos = tuple<long, long>;
+
+vector<Pos>
+read_file(const filesystem::path& filename)
+{
+	ifstream file{ filename };
+
+	vector<Pos> data;
+
+	long x{};
+	long y{};
+	char skip{};
+
+	while ( file >> x >> skip >> y ) {
+		data.emplace_back(x, y);
+	}
+	return data;
+}
+
+void
+part1(const vector<Pos>& data)
+{
+	auto area = numeric_limits<long>::min();
+
+	for ( size_t i = 0; i != data.size(); ++i ) {
+		for ( size_t j = i + 1; j != data.size(); ++j ) {
+			const auto [x1, y1] = data[i];
+			const auto [x2, y2] = data[j];
+
+			const auto width  = abs(x1 - x2) + 1;
+			const auto height = abs(y1 - y2) + 1;
+
+			area = max(area, width * height);
+		}
+	}
+	cout << "Part 1: " << area << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+	auto data = read_file("data/day09.txt");
+	part1(data);
+}
-- 
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