[Kotlin] Selection Sort

지정한 자리에 탐색 범위(비교 대상)에서 찾은 맞는 값(가장 작거나, 가장 크거나)을 찾아 넣는다.

기본 swap

fun <T> ArrayList<T>.swap(firstIndex: Int, secondIndex: Int) {
    val temp = this[firstIndex]
    this[firstIndex] = this[secondIndex]
    this[secondIndex] = temp
}

 

Selection Sort

fun <T: Comparable<T>> ArrayList<T>.selectionSort(showLog: Boolean = true) :ArrayList<T> {

    if (this.size < 2) {
        println("배열 크기 : ${this.size}. 배열 그대로 반환")
        return this
    }

    for (currentPosition in 0 until this.lastIndex) {
        var indexOfMin = currentPosition

        for (indexOfComparison in currentPosition + 1 .. this.lastIndex) {
            if (this[indexOfMin] > this[indexOfComparison]) {
                indexOfMin = indexOfComparison
            }
        }

        if (indexOfMin != currentPosition) {
        this.swap(indexOfMin, currentPosition)
    }

    if (showLog) println("정렬 : $this")
    }

    return this
}

 

Test

fun main() {
    val arrayList = arrayListOf(4, 1, 5, 2, 3)
    testSelectionSort(arrayList)
}

fun <T:Comparable<T>> testSelectionSort(testList: ArrayList<T>) {
    println("input: $testList")
    println("result : ${testList.selectionSort()}")
    println("--------------------------------------------")
}