WIP: implement part 1

src/days/day10.zig

@@ -11,19 +11,18 @@ pub fn run(allocator: std.mem.Allocator) !void {
         ;
 
     var lines = std.mem.tokenizeScalar(u8, input, '\n');
-
-    var machines: std.ArrayList(Machine) = .empty;
-    defer {
-        for (machines.items) |machine| {
-            machine.deinit();
-        }
-        machines.deinit(allocator);
-    }
-
+    var i: usize = 0;
     while (lines.next()) |line| {
+        defer i += 1;
+
         const machine = try Machine.init(allocator, line);
+        defer machine.deinit();
+
         std.debug.print("{f}\n", .{machine});
-        try machines.append(allocator, machine);
+
+        const initial_lights_state: std.bit_set.IntegerBitSet(Machine.MaxLightCount) = .initEmpty();
+        const button_presses = machine.pressButtonSequences(initial_lights_state);
+        std.debug.print("machine {d} required {d} button presses", .{i, button_presses});
     }
 }
 
@@ -35,7 +34,7 @@ const Machine = struct {
 
     const Self = @This();
 
-    const MaxLightCount = 16;
+    pub const MaxLightCount = 16;
 
     pub fn init(allocator: std.mem.Allocator, line: []const u8) !Self {
         std.debug.assert(line[0] == '[');
@@ -84,5 +83,21 @@ const Machine = struct {
             try w.print("({b})", .{button.mask});
         }
     }
+
+    pub fn pressButtonSequences(
+        self: Self,
+        initial_lights_state: std.bit_set.IntegerBitSet(MaxLightCount),
+        buttons_pressed: *usize,
+    ) usize {
+        var button_presses: usize = 0;
+        for (self.buttons) |button| {
+            const result = initial_lights_state.xorWith(button);
+            if (result.mask == self.lights_goal.mask) {
+                return 1;
+            }
+            button_presses += self.pressButtonSequences(result);
+        }
+        return button_presses;
+    }
 };