Kotlin 조합(Combination)

 

fun <T> combination(answer: MutableList<List<T>>, el: List<T>, ck: Array<Boolean>, start: Int, target: Int) {
    if (target == 0) {
        val subset = el.filterIndexed { index, _ -> ck[index] }
        answer.add(subset)
    } else {
        for (i in start until el.size) {
            ck[i] = true
            combination(answer, el, ck, i + 1, target - 1)
            ck[i] = false
        }
    }
}

fun main(args: Array<String>) {
    var arr = listOf(1, 2, 3, 4)    // 1. Int
    //var arr = "asdf".toList()   // 2. String

    for(i in 1 .. arr.size) {
        val answer = mutableListOf<List<Int>>()     // 1. Int
        // val answer = mutableListOf<List<Char>>() // 2. String
        println("================$i 개====================")
        combination(answer, arr, Array<Boolean>(arr.size) { false }, 0,  i)
        answer.forEach { println(it) }
    }

}

combination (
answer : 조합의 결과를 저장하는 이중 리스트,

el : 조합을 구할 원소들의 집합,

ck : 원소 선택 여부를 확인하기 위한 배열,

start : 탐색 시작 인덱스,

target : 구할 조합의 원소 개수

)

-> 해당 예시에서는 for문을 이용, target 값을 바꿔가며 1~4개 선택하였을 경우 존재하는 조합의 결과를 출력 한다.



챰조: https://notepad96.tistory.com/111