From e8f91f0bfb65fc6d2402e8f47270d2ae884ca724 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Sun, 7 Dec 2025 08:49:29 +0100
Subject: aoc 2025, day 7, part 1

---
 2025/src/day07.cpp | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 2025/src/day07.cpp

(limited to '2025')

diff --git a/2025/src/day07.cpp b/2025/src/day07.cpp
new file mode 100644
index 0000000..ca73d87
--- /dev/null
+++ b/2025/src/day07.cpp
@@ -0,0 +1,58 @@
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <set>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+namespace {
+
+vector<string>
+read_file(const filesystem::path& filename)
+{
+	ifstream       file{ filename };
+	vector<string> grid;
+
+	for ( string line; getline(file, line); ) {
+		grid.emplace_back(line);
+	}
+
+	return grid;
+}
+
+void
+part1(const vector<string>& grid)
+{
+	set<size_t> curr;
+	curr.insert(grid[0].find('S'));
+
+	int count = 0;
+	for ( size_t i = 1; i < grid.size(); ++i ) {
+		const auto& row = grid[i];
+
+		auto next = curr;
+
+		for ( const auto pos: curr ) {
+			if ( row[pos] == '^' ) {
+				next.erase(pos);
+				next.insert(pos - 1);
+				next.insert(pos + 1);
+				++count;
+			}
+		}
+
+		curr = next;
+	}
+	cout << "Part 1: " << count << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+	auto grid = read_file("data/day07.txt");
+	part1(grid);
+}
-- 
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