From 0464917d4de2143d3c464d54dc1c5590a541cbea Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Fri, 12 Dec 2025 13:42:16 +0100
Subject: aoc 2025, day 12, quick and dirty solution.. :/

---
 2025/src/day12.cpp | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 2025/src/day12.cpp

(limited to '2025/src')

diff --git a/2025/src/day12.cpp b/2025/src/day12.cpp
new file mode 100644
index 0000000..d6f9277
--- /dev/null
+++ b/2025/src/day12.cpp
@@ -0,0 +1,92 @@
+#include <array>
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <regex>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+namespace {
+
+using Region = tuple<long, long, array<long, 6>>;
+
+tuple<map<long, long>, vector<Region>>
+read_file(const filesystem::path& filename)
+{
+	ifstream       file{ filename };
+	vector<string> lines;
+
+	for ( string line; getline(file, line); ) {
+		lines.emplace_back(line);
+	}
+
+	map<long, long> areas;
+
+	size_t idx = 0;
+	for ( ;; idx += 5 ) {
+		if ( lines.at(idx).at(1) != ':' ) {
+			break;
+		}
+
+		const long num = lines.at(idx).at(0) - '0';
+
+		long count = 0;
+		for ( size_t j = idx + 1; j != idx + 4; ++j ) {
+			count += ranges::count(lines.at(j), '#');
+		}
+
+		areas[num] = count;
+	}
+
+	vector<Region> regions;
+	for ( ; idx != lines.size(); ++idx ) {
+		static const regex rgx(R"(^(\d+)x(\d+):\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)$)");
+
+		smatch match;
+		if ( !regex_match(lines.at(idx), match, rgx) ) {
+			continue;
+		}
+
+		regions.emplace_back(
+		    stol(match[1]), // width
+		    stol(match[2]), // height
+		    array<long, 6>{
+		        stol(match[3]),
+		        stol(match[4]),
+		        stol(match[5]),
+		        stol(match[6]),
+		        stol(match[7]),
+		        stol(match[8]) } // counts
+		);
+	}
+
+	return { areas, regions };
+}
+
+void
+part1(const map<long, long>& areas, const vector<Region>& regions)
+{
+	const auto result = ranges::count_if(regions, [&](const auto& region) {
+		const auto& [width, height, counts] = region;
+
+		long required = 0;
+		for ( size_t i = 0; i != counts.size(); ++i ) {
+			required += counts.at(i) * areas.at(static_cast<long>(i));
+		}
+		return required < width * height;
+	});
+
+	cout << "Part 1: " << result << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+	const auto [areas, regions] = read_file("data/day12.txt");
+	part1(areas, regions);
+}
-- 
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