add scala solution for Permutation-In-String

Author: HangMerlin

May-LeetCoding-Challenge/18-Permutation-In-String/Permutation-In-String.scala

@@ -0,0 +1,22 @@
+//almost the same as Question 17 , we use exists instead of filter to find the first permutation
+object Solution {
+  import scala.collection.mutable._
+
+  def checkInclusion(s1: String, s2: String): Boolean = {
+    val diffMap = HashMap.empty[Char, Int]
+    s1.foreach(updateMap(diffMap, _, 1))
+
+    (0 until s2.length).toList.exists(index => {
+      if (index >= s1.length) updateMap(diffMap, s2(index - s1.length), 1)
+      updateMap(diffMap, s2(index), -1)
+      diffMap.isEmpty
+    })
+  }
+
+  def updateMap(map: HashMap[Char, Int], char: Char, incrementer: Int): Unit =
+    map.get(char) match {
+      case Some(number) if number + incrementer == 0 => map -= char
+      case Some(number)                              => map += (char -> (number + incrementer))
+      case None                                      => map += (char -> incrementer)
+    }
+}