[移动开发]用 Kotlin 实现归并排序

package liwen.zhao

class MergeSort(){
    /**
     * 通过递归，将集合左右两部分不断一分为二，然后进行排序合并
     */
    private fun dichotomyAndmergeSort(arrayList: ArrayList<Int>,l:Int,r:Int){
        if(r-l<=0)
            return
        var mid = (l+r)/2
        dichotomyAndmergeSort(arrayList,l,mid) // 集合左边
        dichotomyAndmergeSort(arrayList,mid+1,r) // 集合右边
        merge(arrayList,l,mid,r)
    }

    private fun merge(arrayList: ArrayList<Int>, l: Int, mid: Int, r: Int) {
        var arrayListCopy: ArrayList<Int> = ArrayList()
        for(c in l..r){
            arrayListCopy.add(arrayList.get(c))
        }

        var i = l
        var j = mid + 1
        for (k in l..r){
            if(i>mid){
                arrayList.set(k,arrayListCopy.get(j-l))
                j++
                continue
            }else if(j>r){
                arrayList.set(k,arrayListCopy.get(i-l))
                i++
                continue
            }
            if(arrayListCopy.get(i-l)<arrayListCopy.get(j-l)){
                arrayList.set(k,arrayListCopy.get(i-l))
                i++
            }else{
                arrayList.set(k,arrayListCopy.get(j-l))
                j++
            }
        }
    }

    fun mergeSort(arrayList: ArrayList<Int>){
        dichotomyAndmergeSort(arrayList,0,arrayList.size-1)
    }
}

fun main(){
    var mergeSortObj = MergeSort()
    var arrlist = arrayListOf(1,23,34,0,2,23,15,4,34)
    mergeSortObj.mergeSort(arrlist)
    print(arrlist)
}