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))