From f5c9d40d2ff42464531ad8473359348646c868c0 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Fri, 5 Dec 2025 08:55:43 +0100
Subject: aoc 2025, day 5, part 1

---
 2025/src/day05.cpp | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 2025/src/day05.cpp

(limited to '2025/src/day05.cpp')

diff --git a/2025/src/day05.cpp b/2025/src/day05.cpp
new file mode 100644
index 0000000..2322948
--- /dev/null
+++ b/2025/src/day05.cpp
@@ -0,0 +1,62 @@
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <regex>
+#include <string>
+#include <tuple>
+#include <vector>
+
+using namespace std;
+
+namespace {
+
+using Range  = tuple<long, long>;
+using Ranges = vector<Range>;
+
+tuple<Ranges, vector<long>>
+read_file(const filesystem::path& filename)
+{
+	static const regex range{ R"(^(\d+)-(\d+)$)" };
+	static const regex single{ R"(^(\d+)$)" };
+
+	ifstream file{ filename };
+
+	Ranges       ranges;
+	vector<long> numbers;
+
+	for ( string line; getline(file, line); ) {
+		smatch match;
+		if ( regex_search(line, match, range) ) {
+			ranges.emplace_back(stol(match[1]), stol(match[2]));
+		}
+		else if ( regex_search(line, match, single) ) {
+			numbers.emplace_back(stol(match[1]));
+		}
+	}
+
+	return { ranges, numbers };
+}
+
+void
+part1(const Ranges& ranges, const vector<long>& numbers)
+{
+	long count = 0;
+	for ( const auto number: numbers ) {
+		for ( const auto [start, end]: ranges ) {
+			if ( number >= start && number <= end ) {
+				++count;
+				break;
+			}
+		}
+	}
+	cout << "Part 1: " << count << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+	const auto [ranges, numbers] = read_file("data/day05.txt");
+	part1(ranges, numbers);
+}
-- 
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