From 756f22d58bb198b8f34589c112e1003614ccdcd6 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Sun, 2 Nov 2025 21:41:58 +0100
Subject: aoc 2017, days 1-20

---
 2017/src/day09.cpp | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)
 create mode 100644 2017/src/day09.cpp

(limited to '2017/src/day09.cpp')

diff --git a/2017/src/day09.cpp b/2017/src/day09.cpp
new file mode 100644
index 0000000..60b0d3b
--- /dev/null
+++ b/2017/src/day09.cpp
@@ -0,0 +1,75 @@
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <iterator>
+#include <string>
+
+using namespace std;
+
+namespace {
+
+string
+remove_garbage(string_view line, int& removed)
+{
+	string result;
+
+	removed = 0;
+	for ( size_t pos = 0; pos < line.size(); ) {
+		if ( line.at(pos) == '<' ) {
+			++pos;
+			while ( pos < line.size() && line.at(pos) != '>' ) {
+				if ( line.at(pos) == '!' ) {
+					pos += 2;
+				}
+				else {
+					++pos;
+					++removed;
+				}
+			}
+			++pos;
+		}
+		else {
+			result += line.at(pos);
+			++pos;
+		}
+	}
+
+	return result;
+}
+
+string
+read_file(const filesystem::path& filename)
+{
+	ifstream file{ filename };
+	return { istreambuf_iterator<char>{ file }, {} };
+}
+
+void
+solve(string_view data)
+{
+	int score   = 0;
+	int depth   = 0;
+	int removed = 0;
+
+	for ( const auto chr: remove_garbage(data, removed) ) {
+		if ( chr == '{' ) {
+			++depth;
+		}
+		else if ( chr == '}' ) {
+			score += depth;
+			--depth;
+		}
+	}
+
+	cout << "Part1: " << score << '\n';
+	cout << "Part2: " << removed << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+	auto data = read_file("data/day09.txt");
+	solve(data);
+}
-- 
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