From b8af8aa8a126b5b966b7d9f50ffec626e8aa1045 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Fri, 17 Jan 2025 14:33:00 +0100
Subject: aoc 2016, day 9

---
 2016/src/day09.cpp | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)
 create mode 100644 2016/src/day09.cpp

(limited to '2016/src/day09.cpp')

diff --git a/2016/src/day09.cpp b/2016/src/day09.cpp
new file mode 100644
index 0000000..e0b0468
--- /dev/null
+++ b/2016/src/day09.cpp
@@ -0,0 +1,72 @@
+#include <fstream>
+#include <iostream>
+
+using namespace std;
+
+string
+read_file(string_view filename)
+{
+	fstream input{ filename };
+	string  line;
+	getline(input, line);
+	return line;
+}
+
+void
+part1(string_view line)
+{
+	size_t len = 0;
+	for ( size_t i = 0; i != line.length(); ) {
+		size_t lhs = 0;
+		size_t rhs = 0;
+
+		if ( sscanf(&line[i], "(%zux%zu)", &lhs, &rhs) == 2 ) {
+			i = line.find(')', i) + 1 + lhs;
+			len += lhs * rhs;
+		}
+		else {
+			++i;
+			++len;
+		}
+	}
+	cout << len << endl;
+}
+
+void
+part2(string_view line)
+{
+	function<size_t(string_view)> part2_rec = [&](string_view line) {
+		size_t len = 0;
+		for ( size_t i = 0; i != line.length(); ) {
+			size_t lhs = 0;
+			size_t rhs = 0;
+
+			if ( sscanf(&line[i], "(%zux%zu)", &lhs, &rhs) == 2 ) {
+				i = line.find(')', i) + 1;
+				len += part2_rec({ &line[i], lhs }) * rhs;
+				i += lhs;
+			}
+			else {
+				++i;
+				++len;
+			}
+		}
+		return len;
+	};
+
+	cout << part2_rec(line) << endl;
+}
+
+int
+main()
+{
+	auto line = read_file("data/day09.txt");
+	// part1("ADVENT");
+	// part1("A(1x5)BC");
+	// part1("(3x3)XYZ");
+	// part1("A(2x2)BCD(2x2)EFG");
+	// part1("(6x1)(1x3)A");
+	// part1("X(8x2)(3x3)ABCY");
+	part1(line);
+	part2(line);
+}
-- 
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