From 61781ca539ffe3514f08b193839687b8c47665b0 Mon Sep 17 00:00:00 2001
From: Mohsin Alam <mohsinalam3851@gmail.com>
Date: Sun, 3 Aug 2025 17:42:37 +0530
Subject: [PATCH] Refactored binarySearch implementation in scala to return
 index instead of value. The updated solution is closer to the one given in
 chapter and is more idiomatic Scala style and standard

---
 .../scala/01_introduction_to_algorithms.scala | 32 +++++++++----------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/01_introduction_to_algorithms/scala/01_introduction_to_algorithms.scala b/01_introduction_to_algorithms/scala/01_introduction_to_algorithms.scala
index 30edf68e..ee5b984f 100644
--- a/01_introduction_to_algorithms/scala/01_introduction_to_algorithms.scala
+++ b/01_introduction_to_algorithms/scala/01_introduction_to_algorithms.scala
@@ -1,18 +1,16 @@
-def binarySearch(list: List[Int], item: Int): Int = {
-  if(list.isEmpty) { println("Item not found"); return 0 }
-  val guessIndex = (list.length) / 2 
-  val guess = list(guessIndex)
-  if(item == guess) guess
-  else if(item < guess){
-    val halfList = list.take(list.length / 2)
-    binarySearch(halfList, item)
-  }
-  else {
-    val halfList = list.drop(1 + (list.length / 2))
-    binarySearch(halfList, item)
-  }
-}
+def binarySearch(numbers : Vector[Int], item : Int) : Option[Int] = {
+    @tailrec
+    def search(low : Int, high : Int) : Option[Int] = {
+      println(s"low = $low ; high = $high")
+      if (low > high) None
+      else{
+        val mid = (low + high)/2
+        val guess = numbers(mid)
+        if (guess == item) Some(mid)
+        else if (guess > item) search(low, mid - 1)
+        else search(mid + 1, high)
+      }
+    }
 
-val myList = List(1,3,5,7,9)
-println(binarySearch(myList, 3))
-println(binarySearch(myList, -1))
+    search(0, numbers.length - 1)
+  }