From c7df2c89969cc78f0e86b090eef64e2cce4e3325 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Tue, 3 Dec 2024 17:41:30 +0100
Subject: aoc 2024, day3

---
 2024/src/day03.cpp | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)
 create mode 100644 2024/src/day03.cpp

(limited to '2024')

diff --git a/2024/src/day03.cpp b/2024/src/day03.cpp
new file mode 100644
index 0000000..5b6ec9e
--- /dev/null
+++ b/2024/src/day03.cpp
@@ -0,0 +1,60 @@
+#include <fstream>
+#include <iostream>
+#include <iterator>
+#include <regex>
+#include <string>
+using namespace std;
+
+string
+read_file(string_view filename)
+{
+	fstream input{ filename };
+	return { istream_iterator<char>{ input }, {} };
+}
+
+void
+part1(const string& data)
+{
+	static const regex pattern(R"(mul\(\d{1,3},\d{1,3}\))");
+
+	long sum = 0;
+	for ( auto it = sregex_iterator(data.begin(), data.end(), pattern); it != sregex_iterator(); ++it ) {
+		long lhs = 0;
+		long rhs = 0;
+		sscanf(it->str().c_str(), "mul(%ld,%ld)", &lhs, &rhs);
+		sum += lhs * rhs;
+	}
+	cout << sum << endl;
+}
+
+void
+part2(const string& data)
+{
+	static const regex pattern(R"(do\(\)|don't\(\)|mul\(\d{1,3},\d{1,3}\))");
+
+	long sum   = 0;
+	bool state = true;
+	for ( auto it = sregex_iterator(data.begin(), data.end(), pattern); it != sregex_iterator(); ++it ) {
+		if ( it->str() == "do()" ) {
+			state = true;
+		}
+		else if ( it->str() == "don't()" ) {
+			state = false;
+		}
+		else if ( state ) {
+			long lhs = 0;
+			long rhs = 0;
+			sscanf(it->str().c_str(), "mul(%ld,%ld)", &lhs, &rhs);
+			sum += lhs * rhs;
+		}
+	}
+	cout << sum << endl;
+}
+
+int
+main()
+{
+	auto data = read_file("data/day03.txt");
+	part1(data);
+	part2(data);
+}
-- 
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