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