fn blockMatches(index: usize, c: u8) -> Bool {
    if index == 0 {
        return c == 66 || c == 79
    }
    if index == 1 {
        return c == 88 || c == 75
    }
    if index == 2 {
        return c == 68 || c == 81
    }
    if index == 3 {
        return c == 67 || c == 80
    }
    if index == 4 {
        return c == 78 || c == 65
    }
    if index == 5 {
        return c == 71 || c == 84
    }
    if index == 6 {
        return c == 82 || c == 69
    }
    if index == 7 {
        return c == 84 || c == 71
    }
    if index == 8 {
        return c == 81 || c == 68
    }
    if index == 9 {
        return c == 70 || c == 83
    }
    if index == 10 {
        return c == 74 || c == 87
    }
    if index == 11 {
        return c == 72 || c == 85
    }
    if index == 12 {
        return c == 86 || c == 73
    }
    if index == 13 {
        return c == 65 || c == 78
    }
    if index == 14 {
        return c == 79 || c == 66
    }
    if index == 15 {
        return c == 69 || c == 82
    }
    if index == 16 {
        return c == 70 || c == 83
    }
    if index == 17 {
        return c == 76 || c == 89
    }
    if index == 18 {
        return c == 80 || c == 67
    }
    if index == 19 {
        return c == 90 || c == 77
    }
    return false
}

fn chooseBlock(c: u8, used: Span<Bool>) -> i32 {
    var index: usize = 0
    while index < 20 {
        if !used[index] && blockMatches(index, c) {
            return index as i32
        }
        index = index + 1
    }
    return -1
}

fn canSpell(word: Span<u8>) -> Bool {
    var used: [20]Bool = [false; 20]
    var i: usize = 0
    while i < std.mem.len(word) {
        let block: i32 = chooseBlock(word[i], used)
        if block < 0 {
            return false
        }
        if used[block as usize] {
            return false
        }
        used[block as usize] = true
        i = i + 1
    }
    return true
}

pub fn main(world: World) -> Void raises {
    if canSpell(std.mem.span("A")) && canSpell(std.mem.span("BARK")) && (!canSpell(std.mem.span("BOOK")) && canSpell(std.mem.span("TREAT"))) && (!canSpell(std.mem.span("COMMON")) && canSpell(std.mem.span("SQUAD")) && canSpell(std.mem.span("CONFUSE"))) {
        check world.out.write("abc blocks ok\n")
    }
}