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和n之间。
scala> def makeArr(n : Int) : Array[Int] = {
| val a = new Array[Int](n);
| val rand = new scala.util.Random();
| for (i <- a) yield rand.nextInt(n);
| }
makeArr: (n: Int)Array[Int]
scala> makeArr(10).foreach(println)
9
8
3
5
9
6
8
8
0
1
scala> def revert(arr : Array[Int]) = {
| for (i <- 0 until (arr.length - 1, 2)) {
| val t = arr(i);
| arr(i) = arr(i + 1);
| arr(i + 1) = t;
| }
| }
revert: (arr: Array[Int])Unit
scala> val a = Array(1, 2, 3, 4, 5);
a: Array[Int] = Array(1, 2, 3, 4, 5)
scala> revert(a);
scala> a.foreach(println);
2
1
4
3
5
scala> def sigNumArr(arr : Array[Int]) = {
| val buf = new ArrayBuffer[Int]();
| buf ++= (for (i <- arr if i > 0) yield i)
| buf ++= (for (i <- arr if i == 0) yield i)
| buf ++= (for (i <- arr if i < 0) yield i)
|
| buf.toArray
| }
sigNumArr: (arr: Array[Int])Array[Int]
scala> val a = Array(1, -2, 0, -3, 0, 4, 5);
a: Array[Int] = Array(1, -2, 0, -3, 0, 4, 5)
scala> val b = sigNumArr(a);
b: Array[Int] = Array(1, 4, 5, 0, 0, -2, -3)
scala> b.foreach(println);
1
4
5
0
0
-2
-3
scala> import scala.collection.mutable.ArrayBuffer
import scala.collection.mutable.ArrayBuffer
scala> import scala.collection.JavaConversions.asScalaBuffer
import scala.collection.JavaConversions.asScalaBuffer
scala>
scala> def timeZoneName() = {
| val arr = java.util.TimeZone.getAvailableIDs();
| val tmp = (for (i <- arr if i.startsWith("America/")) yield {
| i.drop("America/".length)
| })
| scala.util.Sorting.quickSort(tmp)
| tmp
| }
timeZoneName: ()Array[String]
scala> var c = timeZoneName()
scala> c.foreach(println)
5、设置一个映射,其中包含你想要的一些装备,以及它们的价格。然后根据这个映射构建另一个新映射,采用同一组键,但是价格上打9折。
scala> val map = Map("book"->10, "gun"->18, "ipad"->1000)
map: scala.collection.immutable.Map[String,Int] = Map(book -> 10, gun -> 18, ipad -> 1000)
scala> for((k,v) <- map) yield (k, v * 0.9)
res0: scala.collection.immutable.Map[String,Double] = Map(book -> 9.0, gun -> 16.2, ipad -> 900.0)
6、编写一段WordCount函数,统计传入的字符串中单词的个数
scala> def wordCount(str:String)={
| val count = new scala.collection.mutable.HashMap[String, Int]
| for(word <- str.split("\\s+"))
| count(word) = count.getOrElse(word,0) + 1
| count
| }
wordCount: (str: String)scala.collection.mutable.HashMap[String,Int]
scala> wordCount("wo shi zhong guo ren, wo hen hao")
res1: scala.collection.mutable.HashMap[String,Int] = Map(hao -> 1, guo -> 1, wo -> 2, shi -> 1, ren, -> 1, hen -> 1, zhong -> 1)
7、重复上一个练习,使统计后的单词有序
scala> def wordCount(str:String)={
| var count = scala.collection.immutable.SortedMap[String, Int]()
| for(word <- str.split("\\s+"))
| count += (word -> (count.getOrElse(word,0) + 1))
| count
| }
wordCount: (str: String)scala.collection.immutable.SortedMap[String,Int]
scala> wordCount("wo shi zhong guo ren, wo hen hao")
res0: scala.collection.immutable.SortedMap[String,Int] = Map(guo -> 1, hao -> 1, hen -> 1, ren, -> 1, shi -> 1, wo -> 2, zhong -> 1)
8、 重复前一个练习,使用java.util.TreeMap进行实现,并使之适用于Scala API
scala> import scala.collection.JavaConversions.mapAsScalaMap
import scala.collection.JavaConversions.mapAsScalaMap
scala> def wordCount(str:String)={
| var count: scala.collection.mutable.Map[String, Int] = new java.util.TreeMap[String, Int]
| for(word <- str.split("\\s+"))
| count += (word -> (count.getOrElse(word,0) + 1))
| count
| }
wordCount: (str: String)scala.collection.mutable.Map[String,Int]
scala> wordCount("wo shi zhong guo ren, wo hen hao")
res1: scala.collection.mutable.Map[String,Int] = Map(guo -> 1, hao -> 1, hen -> 1, ren, -> 1, shi -> 1, wo -> 2, zhong -> 1)
9、编写一个函数,从一个整型链表中去除所有的零值。
scala> import scala.collection.mutable._
import scala.collection.mutable._
scala> def removeZero(nums : List[Int]):List[Int]={
| nums.filter(_ != 0)
| }
removeZero: (nums: List[Int])List[Int]
scala> removeZero(List(3,4,5,6,0,7,0,0))
res6: List[Int] = List(3, 4, 5, 6, 7)