99 Problems in Scala

99 Problems originated from Prolog [1] but I came across it here [2] where SCala is used to solve the problems.


==03==
def findMe(l:List[Int], i:Int):Int = { if(i==0) l.head else findMe(l drop 1,i-1) }


==04==
l.foldLeft(0) {(a,b) => a+1 }


==05==
def myRev[A](l:List[A]):List[A] = l.foldLeft([List[A]()) { (a,c) => c :: a}


==14==
l.foldLeft(Nil.asInstanceOf[List[Int]]) {(c,a) => (a :: a :: c) }


==15==
def consmore (l:List[Int], count:Int, element:Int):List[Int] = if(count==0) l else consmore(element::l,count-1, element)


==28==
ll=List[List[Int]] = List(List(1, 2), List(1, 2, 3), List(4, 5), List(5), List(3, 4, 5), List(7), List(1, 2, 3, 4, 5), List(1, 2, 3, 4))
val r1=ll.foldLeft(List[(Int,Int)]()) { (a,b) => (b.length,ll indexOf b) :: a}
val r2= r1 sortWith ((t1,t2)=> t1._1 > t2._1)
val finalResult=r2.foldLeft(List[List[Int]]()) { (a,b) => ll(b._2) :: a }


The level of difficulty rises along. So while beeing lazy because I didn't want to solve all 99. I pick P50 as an quick exercise to solving a more complex task with scala.
==50==

class Node(val h:Int, val char:Char){

def this(h:Int) = this(h,'1');

private var left:Node = null

private var right:Node = null

def getLeft() = left

def getRight() = right

def setLeft(k:Node) = {left = k}

def setRight(k:Node) = {right = k}

def setLeftRight(l:Node, r:Node)= {left = l; right = r}

def hasEdge() = left != null || right != null

def isLeaf() = !char.isDigit

override def toString() = h+" L:"+left+" R:"+right

}

import scala.collection.mutable.HashMap

def findFreq(s:String):HashMap[Char,Int] = {
val r=new HashMap[Char,Int];
s.distinct.foreach(x=> r+= (x -> (s count(y => y==x)) ) );
r
}

def sortNodes(a:Node,b:Node) = a.h < b.h

val fr=findFreq(”MISSISSIPPI”)

val t2=(for {b <- fr; fre =b._2; element=b._1 } yield new Node(fre,element)).toList

val r2=t2 sortWith(sortNodes)

def transform(var l:List[Node]) = {

val r=l take 2
if(r.size > 1)
l=new Node(r(1).haeuf+r(2).haeuf)::l

}

Neu gefunden:


[1]http://sites.google.com/site/prologsite/prolog-problems/
[2]http://aperiodic.net/phil/scala/s-99/
[3]https://github.com/etorreborre/s99