aoc 2025, day 7, part 1

1 files changed, 58 insertions, 0 deletions

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);
+}