Scala学习---数组

1.编写一段代码，将a设置为一个n个随机整数的数组，要求随机数介于0（包含）和n（不包含）之间

 /**
   * Created by vito on 2017/1/11.
   */
 object ex1 {
   def main(args: Array[String]): Unit = {
     //从键盘获得输入
     val n = readInt()
     val array = new Array[Int](n)
     for (i <- 0 until array.length) {
       array(i) = (new util.Random).nextInt(n)
     }
     println(array.mkString(","))
   }
 }

2.编写一个循环，将整数数组中相邻的元素置换。例如，Array（1,2,3,4,5）经过置换后变为Array（2,1,4,3,5）

 /**
   * Created by vito on 2017/1/11.
   */
 object ex2 {
   def main(args: Array[String]): Unit = {
     val array = Array(1,2,3,4,5)

     //将步进设置为2
     for (i <- 0 until (array.length, 2)) {
       if (i != array.length - 1) {
         val tmp = array(i)
         array(i) = array(i + 1)
         array(i + 1) = tmp
       }
     }
     println(array.mkString(","))
   }
 }

3.重复前一个练习，不过这一次生成一个新的值交换过的数组。用for/yield。

 /**
   * Created by vito on 2017/1/11.
   */
 object ex3 {
   def main(args: Array[String]): Unit = {
     val array = Array(1, 2, 3, 4, 5)

     val newArray = for (i <- 0 until(array.length)) yield {
       if (i != array.length - 1) {
         if (i % 2 == 0) array(i + 1) else array(i - 1)
       } else {
         array(i)
       }

     }

     println(newArray.mkString(","))
   }
 }

4.如何计算Array[Double]的平均值？

 /**
   * Created by vito on 2017/1/11.
   */
 object ex5 {
   def main(args: Array[String]): Unit = {
     val array = Array(1, 2, 3, 4, 5)

     val avg = array.sum / array.length

     println(avg)
   }
 }

5.创建一个二维数组，将其中一维数组的顺序逆序，并将每个一维数组中的值逆序。

 scala> val dim = List(List(1,2,3), List(1,2,3,4), List(1,2,3,4,5))
 dim: List[List[Int]] = List(List(1, 2, 3), List(1, 2, 3, 4), List(1, 2, 3, 4, 5))

 scala> dim.map(_.reverse).reverse
 res11: List[List[Int]] = List(List(5, 4, 3, 2, 1), List(4, 3, 2, 1), List(3, 2, 1))