Find Number in Array (#9)

geektimus · web-flow · commit 1cb3a0627cbf · 2019-04-09T00:06:03.000+02:00
* Solution to findNumber in array and getNumbers in range challenges
diff --git a/README.md b/README.md
@@ -110,6 +110,11 @@ Write a program that prints the numbers from 1 to 100. But for multiples
 of three print “Fizz” instead of the number and for the multiples of five print 
 “Buzz”. For numbers which are multiples of both three and five print “FizzBuzz
 
+#### Find number in Array
+
+This is a basic problem where we need to find if a number is present on the
+given array.
+
 ## Useful commands
 
 ### Enable scala style check on compile
diff --git a/src/main/scala/com/codingmaniacs/hackerrank/CollectionChallenges.scala b/src/main/scala/com/codingmaniacs/hackerrank/CollectionChallenges.scala
@@ -0,0 +1,39 @@
+package com.codingmaniacs.hackerrank
+
+import scala.annotation.tailrec
+
+object CollectionChallenges {
+
+  def findNumber(arr: Array[Int], k: Int): String = {
+
+    @tailrec
+    def findK(ls: List[Int], n: Int) : String = {
+      ls match {
+        case Nil => "NO"
+        case h :: _ if h == n => "YES"
+        case _ :: tail => findK(tail, n)
+      }
+    }
+
+    findK(arr.toList, k)
+  }
+
+  def findNumbers(start: Int, end: Int, predicate: Int => Boolean) : Array[Int] = {
+    def findNumbersRec(res: List[Int], rem: List[Int], predicate: Int => Boolean) : Array[Int] = {
+      rem match {
+        case Nil => res.toArray
+        case h :: tail if predicate(h) => findNumbersRec(res ::: List(h), tail, predicate)
+        case _ :: tail => findNumbersRec(res, tail, predicate)
+      }
+    }
+
+    findNumbersRec(List(), (start to end).toList, predicate)
+  }
+
+  def oddNumbers(start: Int, end: Int): Array[Int] = {
+    def oddPredicate(h: Int) : Boolean = {
+      h % 2 != 0
+    }
+    findNumbers(start, end, oddPredicate)
+  }
+}
diff --git a/src/test/scala/com/codingmaniacs/hackerrank/CollectionChallengesSpec.scala b/src/test/scala/com/codingmaniacs/hackerrank/CollectionChallengesSpec.scala
@@ -0,0 +1,39 @@
+package com.codingmaniacs.hackerrank
+
+import org.specs2.mutable.Specification
+
+class CollectionChallengesSpec extends Specification {
+  "The number finder" should {
+    "say yes if the a number exist on an array" in {
+      // scalastyle:off magic.number
+      val s = Array(1, 2, 3, 4, 5)
+      // scalastyle:on magic.number
+      val element = 1
+      val expected = "YES"
+      val result = CollectionChallenges.findNumber(s, element)
+      result mustEqual expected
+    }
+
+    "say no if the a number doesn't exist on an array" in {
+      // scalastyle:off magic.number
+      val s = Array(1, 2, 3, 4, 5)
+      // scalastyle:on magic.number
+      val element = 6
+      val expected = "NO"
+      val result = CollectionChallenges.findNumber(s, element)
+      result mustEqual expected
+    }
+  }
+
+  "The odd / even generator" should {
+    "find all the odd numbers between a range" in {
+      val start = 2
+      val end = 5
+      // scalastyle:off magic.number
+      val expected = Array(3, 5)
+      // scalastyle:on magic.number
+      val oddNumbers = CollectionChallenges.oddNumbers(start, end)
+      oddNumbers mustEqual expected
+    }
+  }
+}
