some little fixes. (#9)

scala/src/main/scala/com/shekhargulati/ninetynine_problems/_01_lists/P04.scala

@@ -1,5 +1,7 @@
 package com.shekhargulati.ninetynine_problems._01_lists
 
+import scala.annotation.tailrec
+
 /**
   * Find the number of elements of a list
   */
@@ -10,6 +12,7 @@ object P04 {
   def length1[T](list: List[T]): Int = list.map(_ => 1).sum
 
   def lengthRecursive[T](list: List[T]): Int = {
+    @tailrec
     def rec(list: List[T], length: Int): Int = list match {
       case x :: xs => rec(xs, length + 1)
       case Nil => length

scala/src/main/scala/com/shekhargulati/ninetynine_problems/_01_lists/P08.scala

@@ -9,7 +9,7 @@ import scala.annotation.tailrec
   * <p>
   * <pre>
   * compress(List(a,a,a,a,b,c,c,a,a,d,e,e,e,e))
-  * [a,b,c,d,e]
+  * [a,b,c,a,d,e]
   * </pre>
   */
 object P08 {

scala/src/main/scala/com/shekhargulati/ninetynine_problems/_01_lists/P16.scala

@@ -16,7 +16,7 @@ object P16 {
     if (n == 0) {
       list
     } else {
-      list.zipWithIndex.withFilter(t => if ((t._2 + 1) % n == 0) false else true).map(_._1)
+      list.zipWithIndex.withFilter(t => (t._2 + 1) % n != 0).map(_._1)
     }
   }
 

scala/src/main/scala/com/shekhargulati/ninetynine_problems/_01_lists/P28.scala

@@ -10,7 +10,7 @@ object P28 {
   The objective is to sort the elements of InList according to their length.
   E.g. short lists first, longer lists later, or vice versa
    */
-  def lsort[T](list: List[List[T]]): List[List[T]] = list.sortWith((l1, l2) => l1.length - l2.length < 0)
+  def lsort[T](list: List[List[T]]): List[List[T]] = list.sortBy(_.length)
 
   /*
   Again, we suppose that a list (InList) contains elements that are lists themselves.
@@ -19,8 +19,8 @@ object P28 {
    */
   def lfsort[T](list: List[List[T]]): List[List[T]] =
     lsort(list)
-      .groupBy(l => l.length).values.toList
-      .sortWith((l1, l2) => l1.length - l2.length < 0)
+      .groupBy(_.length).values.toList
+      .sortBy(_.length)
       .flatten
 
 }

scala/src/main/scala/com/shekhargulati/ninetynine_problems/_02_arithmetic/P31.scala

@@ -10,7 +10,7 @@ object P31 {
     if (number < 2)
       false
     else
-      !((2 to Math.sqrt(number).toInt) exists (f => number % f == 0))
+      !((2 to Math.sqrt(number).toInt) exists (number % _ == 0))
 
 
   /**

scala/src/main/scala/com/shekhargulati/ninetynine_problems/_02_arithmetic/P33.scala

@@ -7,6 +7,6 @@ import com.shekhargulati.ninetynine_problems._01_lists.P10
   */
 object P33 {
 
-  def primeFactorsMult(number: Int): List[(Int, Int)] = P10.encode(P32.primeFactors(number)).map { case (t1, t2) => (t2, t1) }
+  def primeFactorsMult(number: Int): List[(Int, Int)] = P10.encode(P32.primeFactors(number)).map(_.swap)
 
 }