Scala练习-归并排序

package day14

import scala.collection.mutable.ArrayBuffer

/**
* Created by doctorq on 2017/6/26.
* 归并排序
*/
object MergeSort extends App {
/**
* 2个有序数组合并，O(n)时间复杂度
*
* @param left
* @param right
* @return
*/
def mergeArray(left: ArrayBuffer[Int], right: ArrayBuffer[Int]): ArrayBuffer[Int] = {
val sortedArray = new ArrayBuffer[Int]()

while (left.size != 0 && right.size != 0) {
val leftItem = left.head
val rightItem = right.head
if (leftItem < rightItem) {
sortedArray.append(leftItem)
left.remove(0)
} else {
sortedArray.append(rightItem)
right.remove(0)
}
}
if (left.size != 0) {
sortedArray.appendAll(left)
} else if (right.size != 0) {
sortedArray.appendAll(right)
}

sortedArray
}

def mergeSort(list: ArrayBuffer[Int]): ArrayBuffer[Int] = {
if (list.size <= 1) return list
var left = ArrayBuffer[Int]()
var right = ArrayBuffer[Int]()
val size = list.size
for (i <- 0 until size) {
if (i < size / 2) {
left.append(list(i))
} else {
right.append(list(i))
}
}

left = mergeSort(left)
right = mergeSort(right)
mergeArray(left, right)
}

def printlnList(sortedHeap: ArrayBuffer[Int]): Unit = {
sortedHeap.foreach(item => print(s"$item "))
println("sorted!")
}

val list = ArrayBuffer(15, 4, 3, 23, 5, 6, 7, 34, 6, 7, 3, 5, 7, 8, 3, 4, 6, 8, 3, 5, 7)

val sortedList = mergeSort(list)

printlnList(sortedList)
}