From a684d9b23822f3ea99a956e076dd1d87dc796c4c Mon Sep 17 00:00:00 2001
From: xeals <dev@xeal.me>
Date: Fri, 15 Dec 2023 17:14:28 +1100
Subject: [PATCH] mild washing

---
 src/day15.zig | 38 +++++++++++---------------------------
 1 file changed, 11 insertions(+), 27 deletions(-)

diff --git a/src/day15.zig b/src/day15.zig
index 866ab54..eec2179 100644
--- a/src/day15.zig
+++ b/src/day15.zig
@@ -17,13 +17,13 @@ const Solution = struct {
 fn hash(input: []const u8) u32 {
     var v: u32 = 0;
     for (input) |c| {
-        v += c;
-        v *= 17;
-        v %= 256;
+        v = ((v + c) * 17) % 256;
     }
     return v;
 }
 
+const SAHM = std.StringArrayHashMap(u8);
+
 fn solve(alloc: mem.Allocator, input: []const u8) !Solution {
     const trimmed = mem.trimRight(u8, input, "\n\r");
 
@@ -34,7 +34,7 @@ fn solve(alloc: mem.Allocator, input: []const u8) !Solution {
         hash_sum += hash(line);
     }
 
-    var boxes: [256]?std.StringArrayHashMap(u8) = [_]?std.StringArrayHashMap(u8){null} ** 256;
+    var boxes: [256]?SAHM = [_]?SAHM{null} ** 256;
     it = util.split(trimmed, ',');
     while (it.next()) |line| {
         if (line.len == 0) continue;
@@ -42,28 +42,17 @@ fn solve(alloc: mem.Allocator, input: []const u8) !Solution {
         const label = line[0..op];
         const label_hash = hash(label);
 
-        // Split init instead of using orelse because references.
-        if (boxes[label_hash] == null) {
-            boxes[label_hash] = std.StringArrayHashMap(u8).init(alloc);
-        }
-        var box = &(boxes[label_hash] orelse unreachable);
+        var box = &(boxes[label_hash] orelse init: {
+            var b = SAHM.init(alloc);
+            boxes[label_hash] = b;
+            break :init b;
+        });
 
         switch (line[op]) {
             '-' => _ = box.orderedRemove(label),
-            '=' => {
-                const focus = try std.fmt.parseInt(u8, line[op + 1 ..], 10);
-                try box.put(label, focus);
-            },
+            '=' => try box.put(label, try std.fmt.parseInt(u8, line[op + 1 ..], 10)),
             else => unreachable,
         }
-
-        // std.debug.print("{s}\n", .{ line });
-        // for (boxes, 0..) |bx, n| {
-        //     if (bx) |b| {
-        //         std.debug.print("box {}: {any} = {any}\n", .{ n, b.keys(), b.values() });
-        //     }
-        // }
-        // std.debug.print("---\n", .{});
     }
 
     var focus: usize = 0;
@@ -72,12 +61,7 @@ fn solve(alloc: mem.Allocator, input: []const u8) !Solution {
         var box_it = box.iterator();
         var lens_n: usize = 1;
         while (box_it.next()) |entry| {
-            const label = entry.key_ptr.*;
-            _ = label;
-            const focal_len = entry.value_ptr.*;
-            const focus_power = box_n * lens_n * focal_len;
-            // std.debug.print("{s}: box {} * slot {} * focal length {} = {}\n", .{ label, box_n, lens_n, focal_len, focus_power });
-            focus += focus_power;
+            focus += box_n * lens_n * entry.value_ptr.*;
             lens_n += 1;
         }
         box.deinit();