From dabcdfc2e135d4bfb6d21468c9211aeb2b80e98a Mon Sep 17 00:00:00 2001
From: Lucia Ceionia <lucia@ceionia.com>
Date: Fri, 6 Dec 2024 01:48:26 -0600
Subject: [PATCH] i don't know why i did that so stupidly this is like 25x
 faster

---
 06/src/main.zig | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/06/src/main.zig b/06/src/main.zig
index a65800f..20bd095 100644
--- a/06/src/main.zig
+++ b/06/src/main.zig
@@ -101,38 +101,36 @@ fn run2(s: []const u8) !u64 {
 
     var map2: [256][256]u8 = undefined;
     @memcpy(&map2, &omap);
-    var prev_states = std.ArrayList(u32).init(alloc);
     y = 0;
     while (y < 256) : (y += 1) {
         if (map[y][2] == 0) continue;
         x = 0;
         while (x < 256) : (x += 1) {
-            // attempt new obstacle... this is ugly and painfully slow
+            // attempt new obstacle... this is ugly
             // but i'm lazy
             if (y == sy and x == sx) continue;
             if (map[y][x] == 'X') {
-                prev_states.clearRetainingCapacity();
                 map2[y][x] = '#';
 
                 var iy = sy;
                 var ix = sx;
                 dy = -1;
                 dx = 0;
+                var dir: u8 = 0;
+                var prev_states: [256][256][4]bool = .{.{.{false}**4}**256}**256;
                 while (map2[iy][ix] != 0) {
-                    const state: u32 = @intCast((@as(usize,@bitCast(dy))<<24)|(@as(usize,@bitCast(dx))<<16)|(iy<<8)|(ix));
-                    const idx = std.mem.indexOfScalar(u32, prev_states.items, state);
-                    if (idx) |_| {
+                    if (prev_states[iy][ix][dir]) {
                         total += 1;
                         break;
                     }
-                    try prev_states.append(state);
+                    prev_states[iy][ix][dir] = true;
                     ny = @intCast(@as(isize,@intCast(iy)) + dy);
                     nx = @intCast(@as(isize,@intCast(ix)) + dx);
                     while (map2[ny][nx] == '#') {
-                        if (dy == -1 and dx == 0) { dy = 0; dx = 1; }
-                        else if (dy == 0 and dx == 1) { dy = 1; dx = 0; }
-                        else if (dy == 1 and dx == 0) { dy = 0; dx = -1; }
-                        else { dy = -1; dx = 0; }
+                        if (dir == 0) { dy = 0; dx = 1; dir = 1; }
+                        else if (dir == 1) { dy = 1; dx = 0; dir = 2; }
+                        else if (dir == 2) { dy = 0; dx = -1; dir = 3; }
+                        else { dy = -1; dx = 0; dir = 0; }
                         ny = @intCast(@as(isize,@intCast(iy)) + dy);
                         nx = @intCast(@as(isize,@intCast(ix)) + dx);
                     }