Solved day 4 part 2. Much easier than part 1...

Signed-off-by: jmug <u.g.a.mariano@gmail.com>

src/day04-2.zig

@@ -0,0 +1,54 @@
+const std = @import("std");
+const print = std.debug.print;
+const process = std.process;
+const fmt = std.fmt;
+const files = @import("lib/files.zig");
+const args = @import("lib/args.zig");
+
+fn solve(search: *[141][141]u8, size: u8) u32 {
+    var total: u32 = 0;
+    for (1..size - 1) |l| {
+        for (1..size - 1) |c| {
+            if (search[l][c] != 'A') {
+                continue;
+            }
+            if (((search[l - 1][c - 1] == 'S' and search[l + 1][c + 1] == 'M') or
+                (search[l - 1][c - 1] == 'M' and search[l + 1][c + 1] == 'S')) and
+                ((search[l + 1][c - 1] == 'S' and search[l - 1][c + 1] == 'M') or
+                (search[l + 1][c - 1] == 'M' and search[l - 1][c + 1] == 'S')))
+            {
+                total += 1;
+            }
+        }
+    }
+    return total;
+}
+
+pub fn main() !void {
+    var margs = process.args();
+    defer margs.deinit();
+    _ = margs.skip();
+
+    const input_path = margs.next() orelse {
+        print("First argument should be the input file\n", .{});
+        return args.ArgError.MissingArguments;
+    };
+    // Only read one dimension, the input is a square matrix.
+    const input_size_str = margs.next() orelse {
+        print("Second argument should be the input size\n", .{});
+        return args.ArgError.MissingArguments;
+    };
+    const input_size = try fmt.parseUnsigned(u8, input_size_str, 10);
+    const input = try files.openForReading(input_path);
+
+    // 140 is the size of the max input.
+    // NOTE: We need one more character than the max line length
+    // Because we're reading directly to the buffer and not using the
+    // result.
+    var word_search: [141][141]u8 = undefined;
+    for (0..input_size) |l| {
+        _ = files.readLine(input, &word_search[l]) catch {};
+    }
+    const total = solve(&word_search, input_size);
+    print("Total X-MAS: {d}\n", .{total});
+}