Complete Precourse-2

BinarySearch.swift

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+//
+//  Untitled.swift
+//  DSA-Practice
+//
+//  Created by Paridhi Malviya on 12/17/25.
+//
+
+/*
+ prerequisites -  the array must be sorted.
+ 2 approaches - iterative bonary search algorithm, recursive binary search algorithm
+ complexity to search for an element - O(log n)
+*/
+
+class BinarySearch {
+
+    init() {
+        let sortedArray = [2, 5, 8, 12, 16, 23, 38, 56, 71, 91]
+        let targetValue = 23
+        if let index = binarySearch(for: targetValue, in: sortedArray) {
+            print("element \(targetValue) found at index \(index)")
+        } else {
+            print("Element \(targetValue) not found in the array")
+        }
+    }
+
+    func binarySearch(for target: Int, in array: [Int]) -> Int? {
+        var left = 0
+        var right = array.count - 1
+        while left <= right {
+            let middle = (left + right) / 2
+            let value = array[middle]
+            if value == target {
+                return middle //target found, return it's index
+            } else if value < target {
+                left = middle + 1 //target is in the right half
+            } else {
+                right = middle - 1 //target is in the left half
+            }
+        }
+        return -1 //Target not found
+    }
+
+    func recursiveBinarySearch(for target: Int, in array: [Int], left: Int = 0, right: Int?) -> Int? {
+
+        let right = right ?? array.count - 1
+
+        guard left < right else {
+            return nil
+        }
+
+        let middle = (left + right) / 2
+        let value = array[middle]
+        if target == value {
+            return middle
+        } else if value < target {
+            return recursiveBinarySearch(for: target, in: array, left: middle + 1, right: right)
+        } else {
+            return recursiveBinarySearch(for: target, in: array, left: left, right: middle - 1)
+        }
+    }
+}