Wikipedia
The McNuggets version of the coin problem was introduced by Henri Picciotto,
who included it in his algebra textbook co-authored with Anita Wah. Picciotto
thought of the application in the 1980s while dining with his son at
McDonald's, working the problem out on a napkin. A McNugget number is
the total number of McDonald's Chicken McNuggets in any number of boxes.
In the United Kingdom, the original boxes (prior to the introduction of
the Happy Meal-sized nugget boxes) were of 6, 9, and 20 nuggets.

Task

Calculate (from 0 up to a limit of 100) the largest non-McNuggets
number (a number n which cannot be expressed with 6x + 9y + 20z = n
where x, y and z are natural numbers).




func maxNugget(limit: Int) -> Int {
  var (max, sixes, nines, twenties, i) = (0, 0, 0, 0, 0)
 
  mainLoop: while i < limit {
    sixes = 0
 
    while sixes * 6 < i {
      if sixes * 6 == i {
        i += 1
        continue mainLoop
      }
 
      nines = 0
 
      while nines * 9 < i {
        if sixes * 6 + nines * 9 == i {
          i += 1
          continue mainLoop
        }
 
        twenties = 0
 
        while twenties * 20 < i {
          if sixes * 6 + nines * 9 + twenties * 20 == i {
            i += 1
            continue mainLoop
          }
 
          twenties += 1
        }
 
        nines += 1
      }
 
      sixes += 1
    }
 
    max = i
    i += 1
  }
 
  return max
}
 
print(maxNugget(limit: 100))