1. import scala.math.random
3. def randomArray(n:Int)={
4. for(i <- 0 until n) yield (random * n).toInt
5. }
7. println(randomArray(10).mkString(","))

1. def reorderArray(arr:Array[Int]):Array[Int]={
2. val t = arr.toBuffer
3. for(i <- 1 until (t.length,2);tmp = t(i);j <- i - 1 until i){
4. t(i) = t(j)
5. t(j) = tmp
6. }
7. t.toArray
8. }
10. println(reorderArray(Array(1,2,3,4,5)).mkString(","
    ))

1. def reorderArray(arr:Array[Int]):Array[Int]={
2. (for(i <- 0 until (arr.length,2)) yield if (i + 1 < arr.length) Array(arr(i + 1),arr(i)) else Array(arr(i))).flatten.toArray
3. }
5. println(reorderArray(Array(1
   ,2,3,4,5)).mkString(","))

1. //使用循環
2. def reorderArray(arr:Array[Int]):Array[Int]={
3. val a = ArrayBuffer[Int]()
4. val b = ArrayBuffer[Int]()
5. arr.foreach(arg => if(arg > 0) a += arg else b += arg)
6. a ++= b
7. a.toArray
8. }

    val a = Array(1,3,-3,-5,-7,3,2)
    def reorderArray(arr: Array[Int]) = {
      val  b = arr.filter(_ > 0)
      val  c = arr.filter(_ <= 0)
      val newarr = b ++ c
      print(newarr.toBuffer.toString())
    }
      reorderArray(a)

1. def aveArray(arr:Array[Double]):Double={
2. arr.sum/arr.length
3. }

1. def reverseArray(arr:Array[Int]):Array[Int]={
2. arr.reverse
3. }

3.7 編寫一段代碼，產出數組中的全部值。去掉反復項。

(提示：查看Scaladoc)
產出數組的代碼就不編寫了。去重僅僅須要調用api就可以
Scala代碼

1. def distinctArray(arr:Array[Int]):Array[Int]={
2. val t = arr.toBuffer
3. t.distinct.toArray
4. }

3.8 又一次編寫3.4節結尾的演示樣例。收集負值元素的下標。反序，去掉最後一個下標。然後對每一個下標調用a.remove(i)。

比較這樣做的效率和3.4節中另外兩種方法的效率

   def removeArray(array: Array[Int]){
      val t = array.toBuffer
      val index = for (i <- 0 until array.length if array(i) < 0) yield i
      val right = index.reverse.dropRight(1)
      right.foreach(t.remove(_))
      print(t)
    }
    
    val a = Array(1,3,-3,-5,-7,3,2,1)
    removeArray(a)

3.9 創建一個由java.util.TimeZone.getAvailableIDs返回ide時區集合，推斷條件是它們在美洲。去掉"America/"前綴並排序

 val americaTimeZone = java.util.TimeZone.getAvailableIDs
val americatimezone = java.util.TimeZone.getAvailableIDs.filter(_.take(8)=="America/")
val sortedamericaTimeZone = americaTimeZone.map(_.drop(8)).sorted

3.10 引入java.awt.datatransfer.並構建一個類型為SystemFlavorMap類型的對象:

val flavors = SystemFlavorMap.getDefaultFlavorMap().asInstanceOf[SystemFlavorMap] 然後以DataFlavor.imageFlavor為參數調用getNativesForFlavor方法。以Scala緩沖保存返回值。 (為什麽用這樣一個晦澀難懂的類？由於在Java標準庫中非常難找到使用java.util.List的代碼)
Scala代碼

1. val flavors = SystemFlavorMap.getDefaultFlavorMap().asInstanceOf[SystemFlavorMap]
2. println(flavors.getNativesForFlavor(DataFlavor.imageFlavor).toArray.toBuffer.mkString(" | ")

快學Scala習題解答—第三章 數組相關操作