advent of code 2023 day 1 part 1 in zig

main.zig

const std = @import("std");

const example =
    \\1abc2
    \\pqr3stu8vwx
    \\a1b2c3d4e5f
    \\treb7uchet
;

pub fn main() !void {
    var it = std.mem.splitScalar(u8, example, '\n');
    var sum: u32 = 0;
    while (it.next()) |line| {
        var first: ?u8 = null;
        var last: ?u8 = null;
        for (line) |byte| {
            if (isDigit(byte)) {
                if (first == null) first = byte;
                last = byte;
            }
        }
        const n = (@as(u32, first.?) - '0') * 10 + (last.? - '0');
        sum += n;
    }
    try std.io.getStdOut().writer().print("{d}\n", .{sum});
}

fn isDigit(byte: u8) bool {
    return switch (byte) {
        '0'...'9' => true,
        else => false,
    };
}