1const std = @import("std");
 2
 3pub fn pt1(input: []const u8) u64 {
 4    var counter: u64 = 0;
 5
 6    var lines = std.mem.splitScalar(u8, input, '\n');
 7
 8    var loop_count: usize = 0;
 9    while (lines.next()) |l| {
10        if (l.len == 0) break;
11        for (0..l.len) |y| {
12            board[loop_count][y] = l[y] == '@';
13        }
14        loop_count += 1;
15    }
16
17    for (0..board.len) |x| {
18        for (0..board[x].len) |y| {
19            if (board[x][y] and countSurround(x, y) < 4) {
20                counter += 1;
21            }
22        }
23    }
24
25    return counter;
26}
27
28pub fn pt2(input: []const u8) u64 {
29    var counter: u64 = 0;
30
31    var lines = std.mem.splitScalar(u8, input, '\n');
32
33    var loop_count: usize = 0;
34    while (lines.next()) |l| {
35        if (l.len == 0) break;
36        for (0..l.len) |y| {
37            board[loop_count][y] = l[y] == '@';
38        }
39        loop_count += 1;
40    }
41
42    var hit = true;
43    while (hit) {
44        hit = false;
45        for (0..board.len) |x| {
46            for (0..board[x].len) |y| {
47                if (board[x][y] and countSurround(x, y) < 4) {
48                    counter += 1;
49                    board[x][y] = false;
50                    hit = true;
51                }
52            }
53        }
54    }
55
56    return counter;
57}
58
59var board: [138][138]bool = undefined;
60fn countSurround(rx: usize, ry: usize) i64 {
61    var count: i64 = 0;
62
63    const min_x = if (rx > 0) rx - 1 else 0;
64    const max_x = if (rx + 1 < board.len) rx + 1 else board.len - 1;
65    const min_y = if (ry > 0) ry - 1 else 0;
66    const max_y = if (ry + 1 < board.len) ry + 1 else board.len - 1;
67
68    for (min_x..max_x + 1) |x| {
69        for (min_y..max_y + 1) |y| {
70            if (x == rx and y == ry) continue; // Skip the center cell
71            if (board[x][y]) count += 1;
72        }
73    }
74
75    return count;
76}
77
78test "Day 4 par 1" {
79    const res = pt1(@embedFile("./input/day4"));
80    try std.testing.expect(res == 1549);
81}
82
83test "Day 4 par 2" {
84    const res = pt2(@embedFile("./input/day4"));
85    try std.testing.expect(res == 8887);
86}