WIP: implement part 2

src/days/day11.zig

@@ -5,6 +5,18 @@ pub const title = "Day 11: Reactor";
 pub fn run(allocator: std.mem.Allocator) !void {
     const input = @embedFile("./input/day11.txt");
     //const input =
+    //    \\aaa: you hhh
+    //    \\you: bbb ccc
+    //    \\bbb: ddd eee
+    //    \\ccc: ddd eee fff
+    //    \\ddd: ggg
+    //    \\eee: out
+    //    \\fff: out
+    //    \\ggg: out
+    //    \\hhh: ccc fff iii
+    //    \\iii: out
+    //    ;
+    //const input =
     //    \\svr: aaa bbb
     //    \\aaa: fft
     //    \\fft: ccc
@@ -49,8 +61,11 @@ pub fn run(allocator: std.mem.Allocator) !void {
         try devices.put(device, outputs_slice);
     }
 
+    var cache: std.StringHashMap(usize) = .init(allocator);
+    defer cache.deinit();
+
     var paths_to_out: usize = 0;
-    visitOutputs("svr", devices, &paths_to_out, false, false);
+    try visitOutputs("svr", "fft", devices, &cache, &paths_to_out);
 
     var buffer: [8]u8 = undefined;
     var stdout_writer = std.fs.File.stdout().writer(&buffer);
@@ -63,30 +78,28 @@ pub fn run(allocator: std.mem.Allocator) !void {
 
 fn visitOutputs(
     start: []const u8,
+    end: []const u8,
     devices: std.StringHashMap([][]const u8),
-    paths_to_out: *usize,
+    cache: *std.StringHashMap(usize),
-    visited_fft: bool,
+    paths_to_end: *usize,
-    visited_dac: bool,
+) !void {
-) void {
+    if (cache.get(start)) |result| {
+        paths_to_end.* += result;
+        return;
+    }
+
+    var paths: usize = 0;
     const device = devices.get(start);
     if (device) |outputs| {
         for (outputs) |output| {
-            if (std.mem.eql(u8, output, "out")) {
+            if (std.mem.eql(u8, output, end)) {
-                std.debug.print("found out! (fft = {any}, dac = {any})\n", .{visited_fft, visited_dac});
+                paths += 1;
-                if (visited_fft and visited_dac) {
-                    std.debug.print("visited fft and dac\n", .{});
-                    paths_to_out.* += 1;
-                }
-            } else if (std.mem.eql(u8, output, "fft")) {
-                std.debug.print("found fft!\n", .{});
-                visitOutputs(output, devices, paths_to_out, true, visited_dac);
-            } else if (std.mem.eql(u8, output, "dac")) {
-                std.debug.print("found dac!\n", .{});
-                visitOutputs(output, devices, paths_to_out, visited_fft, true);
             } else {
-                visitOutputs(output, devices, paths_to_out, visited_fft, visited_dac);
+                try visitOutputs(output, end, devices, cache, &paths);
             }
         }
+        try cache.put(start, paths);
+        paths_to_end.* += paths;
     } else {
         std.debug.print("device {s} not found\n", .{start});
     }