Programming Praxis – McNugget Numbers

In today’s Programming Praxis exercise, our goal is to determine all the numbers that are not McNugget numbers, i.e. numbers that cannot be created by summing multiples of 6, 9 and 20. Let’s get started, shall we?

A quick import:

import Data.List

The code is pretty straightforward: just take all the numbers up to 180 that cannot be created by a linear combination of 6, 9 and 20.

notMcNuggets :: [Integer]
notMcNuggets = [1..180] \\
    [a+b+c | a <- [0,6..180], b <- [0,9..180-a], c <- [0,20..180-a-b]]

To test whether everything works correctly:

main :: IO ()
main = print notMcNuggets

Yup. Nice and simple.

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One Response to “Programming Praxis – McNugget Numbers”

  1. gcbenison Says:

    Here is an alternate implementation where [6,9,20] can be replaced with any list of integers:

    isSumOf (x:[]) y = (mod y x) == 0
    isSumOf (x:xs) y = (any $ isSumOf xs) [y,y-x..0]

    mcNugget = isSumOf [6,9,20]

    *Main Data.List> filter (not . mcNugget) [1..10000]

    *Main Data.List> isSumOf [3852,1171,3257] 91873
    *Main Data.List> isSumOf [3852,1171,3257] 91874

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