快學scala習題（三）

記錄用，避免忘記

1.生成數組，可以用scala提供的scala.util.random方法，該方法提供了nextInt（int）就是用來獲取之間的整數的，具體可查看scaladoc

 def RandArray(n:Int):Array[Int] = {
      var a=new Array[Int](n);
      val s=scala.util.Random;
      for(i<- 0 until a.length){
        a(i)=s.nextInt(n);    
      }
      a;
    }

2.交換數組相鄰元素

 for(i<- 0 until (s.length,2)){
         if(i+1<s.length){
           val t=s(i);
           s(i)=s(i+1)
           s(i+1)=t;

         }

      }

3.用for yield生成新數組

val d=for(i<- 0 until s.length) yield{
         if(i%2==0){
           if(i+1<s.length){
           var t=s(i);
           s(i)=s(i+1);
           s(i+1)=t;
           }
         }
         s(i);
      }

4.記住用clone來保存原始數組

 val s=Array(1,-1,2,4,-3,0,5);
      println("hello world");
      val d=for(i<- 0 until s.length;if(s(i)>0)) yield{
          i;
      }
      val e=for(i<- 0 until s.length;if(s(i)<=0)) yield{

        i;
      }
      var m=0;var n=0;val f=s.clone();
     val g=for(i<- 0 until s.length) yield{

         if(m<d.length){
           s(i)=f(d(m));
           m=m+1;
         }else{
           s(i)=f(e(n));
           n=n+1;
         }
         s(i);
      }
      for(i<- 0 until g.length){
        println(g(i));

      }

5.計算array的平均值

  var avg=0;
      for(i<- 0 until g.length){
        avg=avg+g(i);

      }
    avg=avg/g.length.toDouble

6.只需要使用reverse即可，列子：a.reverse

7.去掉數組中重複項使用distinct方法即可

8.

 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)

9.

val s=java.util.TimeZone.getAvailableIDs;
      val e=for(i<- 0 until s.length;if s(i).contains("America/")) yield{
          s(i).diff("America/");

      }
    e.sorted.foreach {println(_)}

10.

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