Merge pull request #1229 from yadavan88/power-of-2

Added codeto check if a number is power of 2

Author: dominiqueplante

build.sbt

@@ -116,7 +116,8 @@ lazy val scala_core_9 = (project in file("scala-core-modules/scala-core-9"))
   .settings(
     name := "scala-core-9",
     libraryDependencies ++= scalaTestDeps,
-    scalaVersion := scala3Version
+    scalaVersion := scala3Version,
+    libraryDependencies += "org.scalatestplus" %% "scalacheck-1-17" % "3.2.18.0" % Test
   )
 
 lazy val scala_core_io = (project in file("scala-core-modules/scala-core-io"))

scala-core-modules/scala-core-9/src/main/scala/com/baeldung/scala/powerof2/PowerOfTwo.scala

@@ -0,0 +1,29 @@
+package com.baeldung.scala.powerof2
+
+import scala.annotation.tailrec
+
+object PowerOfTwo {
+
+  def isPowerOfTwoByDivision(num: Long): Boolean = {
+    @tailrec
+    def isPowerRec(n: Long): Boolean = {
+      if (n == 1) true
+      else if (n % 2 == 0) isPowerRec(n / 2)
+      else false
+    }
+    num > 0 && isPowerRec(num)
+  }
+
+  def isPowerOfTwoByCountingOnes(num: Long): Boolean = {
+    num > 0 && num.toBinaryString.count(_ == '1') == 1
+  }
+
+  def isPowerOfTwoByBitwiseAnd(num: Long): Boolean = {
+    num > 0 && (num & (num - 1)) == 0
+  }
+
+  def isPowerOfTwoByLazyList(num: Long): Boolean = {
+    num > 0 && LazyList.iterate(num)(_ / 2).takeWhile(_ > 1).forall(_ % 2 == 0)
+  }
+
+}

scala-core-modules/scala-core-9/src/test/scala/com/baeldung/scala/powerof2/PowerOfTwoUnitTest.scala

@@ -0,0 +1,48 @@
+package com.baeldung.scala.powerof2
+
+import org.scalacheck.Gen
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+import org.scalatestplus.scalacheck.ScalaCheckPropertyChecks
+
+class PowerOfTwoUnitTest
+  extends AnyFlatSpec
+  with Matchers
+  with ScalaCheckPropertyChecks {
+
+  private val powerOfTwoFunctions = Seq(
+    ("Division", PowerOfTwo.isPowerOfTwoByDivision),
+    ("Counting Ones", PowerOfTwo.isPowerOfTwoByCountingOnes),
+    ("Bitwise AND", PowerOfTwo.isPowerOfTwoByBitwiseAnd),
+    ("LazyList", PowerOfTwo.isPowerOfTwoByLazyList)
+  )
+
+  powerOfTwoFunctions.foreach { (desc, fn) =>
+    it should s"[$desc] return true for a number that is power of 2" in {
+      val powersOfTwo: Gen[Long] =
+        Gen.choose(0, 62).map(n => Math.pow(2, n).toLong)
+      forAll(powersOfTwo) { num =>
+        fn(num) shouldBe true
+      }
+    }
+
+    it should s"[$desc] return false for a number that is NOT a power of 2" in {
+      val powersOfTwo: Gen[Long] =
+        Gen.choose(0, 62).map(n => Math.pow(2, n).toLong)
+      val notPowerOf2 = Gen
+        .choose(0L, Long.MaxValue)
+        .suchThat(n => !powersOfTwo.sample.contains(n))
+      forAll(notPowerOf2) { num =>
+        fn(num) shouldBe false
+      }
+    }
+
+    it should s"[$desc] return false for any negative numbers" in {
+      val negativeNumbers = Gen.choose(Long.MinValue, 0L)
+      forAll(negativeNumbers) { num =>
+        fn(num) shouldBe false
+      }
+    }
+  }
+
+}