src/days/day04.zig

@@ -1,77 +1,46 @@
 const std = @import("std");
 
-pub const title = "Day 04: Printing Department";
+pub const title = "Day 04";
 
 pub fn run(_: std.mem.Allocator) !void {
-    const initial_input = @embedFile("./input/day04.txt");
-    //const initial_input =
-    //    \\..@@.@@@@.
-    //    \\@@@.@.@.@@
-    //    \\@@@@@.@.@@
-    //    \\@.@@@@..@.
-    //    \\@@.@@@@.@@
-    //    \\.@@@@@@@.@
-    //    \\.@.@.@.@@@
-    //    \\@.@@@.@@@@
-    //    \\.@@@@@@@@.
-    //    \\@.@.@@@.@.
-    //    ;
-
-    const input: []u8 = @constCast(initial_input);
+    const input = @embedFile("./input/day04.txt");
+    var lines = std.mem.tokenizeScalar(u8, input, '\n');
 
     var accumulator: u32 = 0;
 
-    while (true) {
-        std.debug.print("{s}\n", .{input});
+    var previous_line: ?[]const u8 = null;
+    while (lines.next()) |line| {
+        const next_line = lines.peek();
 
-        var rolls_removed: u32 = 0;
+        if (previous_line) |p| std.debug.assert(line.len == p.len);
+        if (next_line) |n| std.debug.assert(line.len == n.len);
 
-        var lines = std.mem.tokenizeScalar(u8, input, '\n');
+        for (line, 0..) |c, i| {
+            if (c != '@') continue;
 
-        var previous_line: ?[]const u8 = null;
-        var line_index: usize = 0;
-        while (lines.next()) |line| {
-            const next_line = lines.peek();
+            var rolls: u8 = 0;
 
-            if (previous_line) |p| std.debug.assert(line.len == p.len);
-            if (next_line) |n| std.debug.assert(line.len == n.len);
-
-            for (line, 0..) |c, i| {
-                if (c != '@') continue;
-
-                var rolls: u8 = 0;
-
-                if (previous_line) |p| {
-                    if (i > 0 and p[i - 1] == '@') rolls += 1;
-                    if (p[i] == '@') rolls += 1;
-                    if (i < p.len - 1 and p[i + 1] == '@') rolls += 1;
-                }
-
-                if (i > 0 and line[i - 1] == '@') rolls += 1;
-                if (i < line.len - 1 and line[i + 1] == '@') rolls += 1;
-
-                if (next_line) |n| {
-                    if (i > 0 and n[i - 1] == '@') rolls += 1;
-                    if (n[i] == '@') rolls += 1;
-                    if (i < n.len - 1 and n[i + 1] == '@') rolls += 1;
-                }
-
-                if (rolls < 4) {
-                    input[(line_index * (line.len + 1)) + i] = 'x';
-                    rolls_removed += 1;
-                }
+            if (previous_line) |p| {
+                if (i > 0 and p[i - 1] == '@') rolls += 1;
+                if (p[i] == '@') rolls += 1;
+                if (i < p.len - 1 and p[i + 1] == '@') rolls += 1;
             }
 
-            previous_line = line;
-            line_index += 1;
+            if (i > 0 and line[i - 1] == '@') rolls += 1;
+            if (i < line.len - 1 and line[i + 1] == '@') rolls += 1;
+
+            if (next_line) |n| {
+                if (i > 0 and n[i - 1] == '@') rolls += 1;
+                if (n[i] == '@') rolls += 1;
+                if (i < n.len - 1 and n[i + 1] == '@') rolls += 1;
+            }
+
+            if (rolls < 4) {
+                accumulator += 1;
+            }
         }
 
-        std.debug.print("removed {d} rolls\n", .{rolls_removed});
-        if (rolls_removed > 0) {
-            accumulator += rolls_removed;
-        } else {
-            break;
-        }
+        previous_line = line;
     }
 
     var buffer: [8]u8 = undefined;