exercism/zig/isogram/isogram.zig

pub const std = @import("std");

pub fn cmp(context: void, a: u8, b: u8) bool {
    _ = context;
    if (a < b) {
        return true;
    }
    return false;
}

pub fn isIsogram(str: []const u8) bool {
    const len = str.len;
    if (len == 0) return true;

    var buf = [_]u8{0} ** 256;
    const lower = std.ascii.lowerString(&buf, str);
    std.mem.sort(u8, lower, {}, cmp);

    for (0..len - 1) |i| {
        if (lower[i] == lower[i + 1] and std.ascii.isAlphabetic(lower[i])) {
            return false;
        }
    }

    return true;
}