Solutions in Scala

scala/0217-contains-duplicate.scala

@@ -2,11 +2,18 @@ import scala.collection.mutable.HashSet
 
 object Solution {
   def containsDuplicate(nums: Array[Int]): Boolean = {
-    var seen: HashSet[Int] = HashSet() 
+    var seen: HashSet[Int] = HashSet()
     for (num <- nums) {
       if (seen.contains(num)) return true
       seen.add(num)
     }
     return false
   }
+
+  // using group by and filter
+  def containDupsOneLiner(nums: Array[Int]): Boolean = {
+    val dups = nums.groupBy(identity).filter(grps => grps._2.length > 1)
+    dups.nonEmpty
+  }
+
 }

scala/0238-product-of-array-except-self.scala

@@ -0,0 +1,20 @@
+object Solution {
+    def productExceptSelf(nums: Array[Int]): Array[Int] = {
+
+        val result = Array.fill[Int](nums.length)(1)
+
+        var prefix = 1
+        for(i <- nums.indices) {
+            result(i) = prefix
+            prefix = prefix * nums(i)
+        }
+
+        var postfix = 1
+        for(i <- nums.length-1 to 0 by -1) {
+            result(i) = result(i) * postfix
+            postfix = postfix * nums(i)
+        }
+
+        result
+    }
+}

scala/0242-valid-anagram.scala

@@ -30,4 +30,21 @@ object Solution {
 
     return true
   }
+
+  //by maintaing an array of length 26 and using only 1 for loop
+  def isAnagram2(s: String, t: String): Boolean = {
+    if(s.length != t.length)
+      return false
+
+    val arr = Array.fill[Int](26)(0)
+
+    val idx = (ch: Char) => ch - 'a'  // can alternatively be written as: val idx = (_: Char) - 'a'
+
+    for (i <- s.indices) {
+      arr(idx(s(i))) += 1
+      arr(idx(t(i))) -= 1
+    }
+
+    arr.forall(_ == 0)
+  }
 }

scala/0347-top-k-frequent-elements.scala

@@ -16,4 +16,17 @@ object Solution {
 
         map
     }
+
+    // using `groupBy` and only `one` Mutable Collection.
+    def topKFrequent2(nums: Array[Int], k: Int): Array[Int] = {
+
+        val frequencyArray = Array.fill(nums.length + 1)(ArrayBuffer.empty[Int])
+
+        val groupedNums = nums.groupBy(identity).mapValues(_.length)
+
+        groupedNums.foreach { case (num, len) => frequencyArray(len) += num }
+
+        frequencyArray.flatten.takeRight(k)
+
+    }
 }