46 lines
1.3 KiB
Kotlin
46 lines
1.3 KiB
Kotlin
class CombinationIterator(val characters: String, val combinationLength: Int) {
|
|
private var indices = (0 until combinationLength).toMutableList()
|
|
|
|
private fun nextCombination(index: Int) {
|
|
// bump the current index
|
|
indices[index]++
|
|
|
|
// we have gone through the whole string
|
|
while (indices[index] == characters.length && index > 0) {
|
|
// bump the previous index
|
|
nextCombination(index - 1)
|
|
|
|
// set current index to previous + 1, since it must be the following one
|
|
indices[index] = indices[index - 1] + 1
|
|
}
|
|
}
|
|
|
|
// By default bumping just the last index
|
|
private fun nextCombination() = nextCombination(combinationLength - 1)
|
|
|
|
private fun getCombination(): String =
|
|
indices.map { characters[it] }.joinToString(separator="")
|
|
|
|
fun next(): String {
|
|
// construct the combination
|
|
val combination = getCombination()
|
|
|
|
// bump the combination
|
|
nextCombination()
|
|
|
|
return combination
|
|
}
|
|
|
|
fun hasNext(): Boolean =
|
|
indices.all {
|
|
it < characters.length
|
|
}
|
|
|
|
}
|
|
|
|
/**
|
|
* Your CombinationIterator object will be instantiated and called as such:
|
|
* var obj = CombinationIterator(characters, combinationLength)
|
|
* var param_1 = obj.next()
|
|
* var param_2 = obj.hasNext()
|
|
*/
|