CODEWITHSUNDEEP
androidandroid-studiokotlin
Maff
Maff

Reputation: 439

Set of random numbers between x and y, needs to be unique, using Kotlin

in Kotlin, I'm trying to, for example, get 5 numbers into an Array, List or ArrayList, the 5 numbers to come from 6 to 30. Been looking online and I ended up getting the following to work, however it isn't picking unique numbers for the list, so it could pick something like 6,6,20,24,24.

val cardNumbersCol1 = (1..5).map { (6..30).random() }

Is there a better way to do this?

I'm still learning as I go.

Thanks

Upvotes: 1

Views: 1131

Answers (3)

Natig Babayev
Natig Babayev

Reputation: 3305

Option 1: You can create Set because set cannot have duplicate elements by definition. Therefore, you won't need to worry about duplicate numbers:

val cardNumbersCol1 = mutableSetOf<Int>()

while (cardNumbersCol1.size != 5) {
    cardNumbersCol1.add(Random.nextInt(6, 30))
}

Option 2: You can generate range from 6 to 30 use shuffled() function to shuffle the list. Finally, you can take first 5 items from the list and they'll be unique also:

val cardNumbersCol1 = (6..30).shuffled().take(5).toSet()

Upvotes: 2

Todd
Todd

Reputation: 31710

Another approach is to use a sequence generator to produce a sequence of random Ints, and then filter by distinct and take the first few that you want:

fun randomGenerator(from: Int, 
                    until: Int, 
                    random: Random = Random.Default): Sequence<Int> = sequence {
    while(true) {
        yield(random.nextInt(from, until))
    }
}

fun main() {
    val someRandomInts: Set<Int> =
        randomGenerator(6, 30)
            .distinct()
            .take(5)
            .toSet()
    println(someRandomInts)
}

Or, you can define an extension function on IntRange to make this a bit prettier:

fun IntRange.randomSequence(random: Random = Random.Default): Sequence<Int> = sequence {
    while(true) {
        yield([email protected](random))
    }
}

And to use:

val someRandomInts: Set<Int> =
    (6..30).randomSequence().distinct().take(5).toSet()

Upvotes: 2

S-Sh
S-Sh

Reputation: 3893

You can populate set with manual checking items:

var cardNumbersCol1 = mutableSetOf<Int>()
while (cardNumbersCol1.size < 5) {
  val item = (6..30).random()
  cardNumbersCol1.add(item)
}

Upvotes: 1

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