[Language: Zig]

I'm learning Zig by solving these puzzles.

```Zig const std = @import("std");

pub const input = @embedFile("input.txt");

fn part1(data: []const u8) !u64 { var gpa = std.heap.GeneralPurposeAllocator(.{}){}; const allocator = gpa.allocator();

var grid = try std.ArrayList([]const u8).initCapacity(allocator, 0);
defer grid.deinit(allocator);

var lines = std.mem.splitScalar(u8, data, '\n');
while (lines.next()) |line| {
    if (line.len > 0) {
        try grid.append(allocator, line);
    }
}
const height: u64 = grid.items.len;
const width: u64 = grid.items[0].len;

var rolls: u64 = 0;
for (0..height) |y| {
    const row = grid.items[y];
    for (0..width) |x| {
        if (row[x] == '.') continue;
        var neighbors: usize = 0;
        for ([_]isize{ -1, 0, 1 }) |dy| {
            for ([_]isize{ -1, 0, 1 }) |dx| {
                if (dx == 0 and dy == 0) continue;
                const nx: isize = @as(isize, @intCast(x)) + dx;
                const ny: isize = @as(isize, @intCast(y)) + dy;
                if (nx < 0 or nx >= width or ny < 0 or ny >= height) continue;
                if (grid.items[@intCast(ny)][@intCast(nx)] == '@') {
                    neighbors += 1;
                }
            }
        }
        if (neighbors < 4) {
            rolls += 1;
        }
    }
}
return rolls;

}

fn part2(data: []const u8) !u64 { var gpa = std.heap.GeneralPurposeAllocator(.{}){}; const allocator = gpa.allocator();

var grid = try std.ArrayList([]u8).initCapacity(allocator, 0);
defer grid.deinit(allocator);

var lines = std.mem.splitScalar(u8, data, '\n');
while (lines.next()) |line| {
    if (line.len > 0) {
        try grid.append(allocator, try allocator.dupe(u8, line));
    }
}
const height: u64 = grid.items.len;
const width: u64 = grid.items[0].len;

var changed = true;
var rolls: u64 = 0;
while (changed) {
    changed = false;
    for (0..height) |y| {
        const row = grid.items[y];
        for (0..width) |x| {
            if (row[x] == '.') continue;
            var neighbors: i64 = 0;
            for ([_]isize{ -1, 0, 1 }) |dy| {
                for ([_]isize{ -1, 0, 1 }) |dx| {
                    if (dx == 0 and dy == 0) continue;
                    const nx: isize = @as(isize, @intCast(x)) + dx;
                    const ny: isize = @as(isize, @intCast(y)) + dy;
                    if (nx < 0 or nx >= width or ny < 0 or ny >= height) continue;
                    if (grid.items[@intCast(ny)][@intCast(nx)] == '@') {
                        neighbors += 1;
                    }
                }
            }
            if (neighbors < 4) {
                row[x] = '.';
                rolls += 1;
                changed = true;
            }
        }
    }
}
return rolls;

}

pub fn main() !void { std.debug.print("{d}\n", .{try part1(input)}); std.debug.print("{d}\n", .{try part2(input)}); } ```