Finish day11, part 2

src/days/day11.zig

@@ -63,15 +63,29 @@ pub fn run(allocator: std.mem.Allocator) !void {
 
     var cache: std.StringHashMap(usize) = .init(allocator);
     defer cache.deinit();
+    try cache.ensureTotalCapacity(devices.count());
 
-    var paths_to_out: usize = 0;
-    try visitOutputs("svr", "fft", devices, &cache, &paths_to_out);
+    const dac_to_fft = try visitOutputs("dac", "fft", devices, &cache);
+    const svr_to_fft = try visitOutputs("svr", "fft", devices, &cache);
+    cache.clearRetainingCapacity();
+
+    const to_fft = if (dac_to_fft == 0) svr_to_fft else dac_to_fft;
+
+    const dac_start = if (dac_to_fft == 0) "fft" else "svr";
+    const end_start = if (dac_to_fft == 0) "dac" else "fft";
+
+    const to_dac = try visitOutputs(dac_start, "dac", devices, &cache);
+    cache.clearRetainingCapacity();
+
+    const to_end = try visitOutputs(end_start, "out", devices, &cache);
+
+    const result = to_fft * to_dac * to_end;
 
     var buffer: [8]u8 = undefined;
     var stdout_writer = std.fs.File.stdout().writer(&buffer);
     const stdout = &stdout_writer.interface;
 
-    try stdout.print("{d}\n", .{paths_to_out});
+    try stdout.print("{d}\n", .{result});
 
     try stdout.flush();
 }
@@ -81,11 +95,9 @@ fn visitOutputs(
     end: []const u8,
     devices: std.StringHashMap([][]const u8),
     cache: *std.StringHashMap(usize),
-    paths_to_end: *usize,
-) !void {
+) !usize {
     if (cache.get(start)) |result| {
-        paths_to_end.* += result;
-        return;
+        return result;
     }
 
     var paths: usize = 0;
@@ -95,13 +107,14 @@ fn visitOutputs(
             if (std.mem.eql(u8, output, end)) {
                 paths += 1;
             } else {
-                try visitOutputs(output, end, devices, cache, &paths);
+                paths += try visitOutputs(output, end, devices, cache);
             }
         }
         try cache.put(start, paths);
-        paths_to_end.* += paths;
+        return paths;
     } else {
         std.debug.print("device {s} not found\n", .{start});
+        return 0;
     }
 }