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iOS

Posted by Roland O'Donnell
Roland O'Donnell
5,667 Points

Need help with creating a func! I'm stuck

ok so I've created the following func.. it randomly selects 6 numbers out of 45 like a lotto draw. but now what i want to do is repeat this process until it draws out the 6 numbers i have chosen in no particular order. simulating how many lotto draws it will take for my numbers to come out, the odds are 1 in 8,145,060. I'm stuck on how to loop my for in loop thanks

 func lotto() -> [Int] {

    var result: [Int] = []

    for eachNumber in 1...6 {

        result.append(Int(arc4random_uniform(45)))

    }
    return result
}

lotto()
Roland O'Donnell
Roland O'Donnell
5,667 Points

in swift code :)

2 Answers

Damien Watson
Damien Watson
27,419 Points

Hey Roland,

I had a crack at doing something like what you asked. Warning that this may cause an infinite loop, which is why I have it only looping until a max number. I have added keepLooping where you can comment out the line below if you want to tempt fate.

My idea is just to get the random 6 numbers, sort them, compare to your sorted numbers and if the same, stop the loop.

func lotto() -> [Int] {
    var result: [Int] = []
    for _ in 1...6 {
        result.append(Int(arc4random_uniform(45)))
    }
    return result
}

func bubbleSort(numbers: [Int]) -> [Int] {
    var listOfNumbers: [Int] = numbers
    let nElements = listOfNumbers.count
    var didSwap = true
    while didSwap {
        didSwap = false

        for i in 0..<nElements - 1 {
            if listOfNumbers[i] < listOfNumbers[i+1] {
                let tmp = listOfNumbers[i]
                listOfNumbers[i] = listOfNumbers[i+1]
                listOfNumbers[i+1] = tmp
                didSwap = true
            }
        }
    }
    return listOfNumbers
}

var myList: [Int] = [41, 35, 18, 15, 7, 2]

var max = 10
var i = 0
var keepLooping = true

//while keepLooping {
while i < max {
    var randomNumbers: [Int] = bubbleSort(lotto())
    i += 1
    if myList == randomNumbers {
        print("Found after \(i) attempts")
        keepLooping = false
    }
}
Roland O'Donnell
Roland O'Donnell
5,667 Points

Im only starting to learn swift code so I'm a novice. trying to figure out what things do is hard sometimes..can you tell me what the bubbleSort func does? i just did this and it works ok i think..

func lotto () -> Set<Int> {

var numbersDrawn: Set<Int> = []

for _ in 1...6 {

    numbersDrawn.insert(Int(arc4random_uniform(45)))
}

return numbersDrawn

}

var myList: Set<Int> = [6,10,21,28,29,35]

var max = 10000 var i = 0 var keepLooping = true

//while keepLooping { while i < max { var randomNumbers: Set<Int> = lotto() i += 1 if myList == randomNumbers { print("(randomNumbers) Found after (i) attempts") keepLooping = false } else { print ("(randomNumbers)") } }

Damien Watson
Damien Watson
27,419 Points

WIth the Bubble sort code, the theory of bubble sort is that the highest number 'floats' to the top, like a bubble I guess. It checks the current item against the next and swaps if smaller, then repeats. It's a really slow process, so changing to a 'set' should improve speeds significantly if you don't need to sort. :)

Roland O'Donnell
Roland O'Donnell
5,667 Points
Roland O'Donnell
Roland O'Donnell
5,667 Points

yes that works. Thank you so much. only thing i changed was the instead of using ordered arrays i just changed them to to a Set as they don't need to be in an exact order.

Damien Watson
Damien Watson
27,419 Points

Ok, cool. Never heard of 'Set', thats a pretty cool thing, quicker than arrays and can only hold unique elements.

Given that, your random list may not contain 6 numbers, as if it pulls the same number twice, it will only be stored once. Unique numbers are what you want though if writing a lotto app. maybe change your code to repeat until the set contains 6 numbers:

func lotto () -> Set<Int> {
  var numbersDrawn: Set<Int> = []
  var i = 0  
  while numbersDrawn.count < 6 {
    numbersDrawn.insert(Int(arc4random_uniform(45)))
  }
  return numbersDrawn
}