change '01_introduction_to_algorithms/Golang/BinarySearch.go'

01_introduction_to_algorithms/Golang/BinarySearch.go

@@ -2,43 +2,55 @@ package main
 
 import "fmt"
 
-func checkBin(list []int, i int) int {
+func checkBin(list []int, i int) interface{} {
+	// low and high keep track of which part of the list you'll search in.
 	low := 0
 	high := len(list) - 1
+	// While you haven't narrowed it down to one element ...
 	for low <= high {
+		// ... check the middle element
 		mid := (low + high) / 2
+		// Found the item.
 		if list[mid] == i {
 			return mid
 		}
-		if list[mid] < i {
-			low = mid + 1
-		} else {
+		// The guess was too high.
+		if list[mid] > i {
 			high = mid - 1
+		// The guess was too low.
+		} else {
+			low = mid + 1
 		}
 	}
-	return -1
+	// Item doesn't exist
+	return nil
 }
 
-func RecursiveCheckBin(list []int, item int, high, low int) int {
+func recursiveCheckBin(list []int, item int, high, low int) interface{} {
+	// Check base case
 	if high >= low {
 		mid := (high + low) / 2
-
+		// If element is present at the middle itself
 		if list[mid] == item {
 			return mid
+		// If element is smaller than mid, then it can only 
+        // be present in left subarray
 		} else if list[mid] > item {
-			return RecursiveCheckBin(list, item, mid-1, low)
+			return recursiveCheckBin(list, item, mid - 1, low)
+		// Else the element can only be present in right subarray 
 		} else {
-			return RecursiveCheckBin(list, item, high, mid+1)
+			return recursiveCheckBin(list, item, high, mid + 1)
 		}
 
 	}
-	return -1
+	// Element is not present in the array 
+	return nil
 }
-
+// you can run this code on: https://go.dev/play/
 func main() {
-	list := []int{1, 2, 3, 4, 5}
-	fmt.Println(checkBin(list, 2))                                          // 0
-	fmt.Println(checkBin(list, -1))                                         // -1
-	fmt.Println(RecursiveCheckBin([]int{1, 2, 3, 4, 5}, 2, len(list)-1, 0)) // 1
-	fmt.Println(RecursiveCheckBin([]int{1, 2, 3, 4, 5}, 0, len(list)-1, 0)) //-1
+	list := []int{1, 3, 5, 7, 9}
+	fmt.Println(checkBin(list, 3))							// => 1
+	fmt.Println(checkBin(list, -1))							// => <nil>
+	fmt.Println(recursiveCheckBin(list, 3, len(list)-1, 0)) // => 1
+	fmt.Println(recursiveCheckBin(list, -1, len(list)-1, 0)) // => <nil>
 }