From 934c305c610fc7e847eae1a43a09126260766be8 Mon Sep 17 00:00:00 2001
From: "go-interview-practice-bot[bot]"
 <230190823+go-interview-practice-bot[bot]@users.noreply.github.com>
Date: Mon, 27 Oct 2025 09:45:39 +0000
Subject: [PATCH] Add solution for Challenge 21

---
 .../krypton-io/solution-template.go           | 152 ++++++++++++++++++
 1 file changed, 152 insertions(+)
 create mode 100644 challenge-21/submissions/krypton-io/solution-template.go

diff --git a/challenge-21/submissions/krypton-io/solution-template.go b/challenge-21/submissions/krypton-io/solution-template.go
new file mode 100644
index 000000000..98d03eee7
--- /dev/null
+++ b/challenge-21/submissions/krypton-io/solution-template.go
@@ -0,0 +1,152 @@
+package main
+
+import (
+	"fmt"
+)
+
+func main() {
+	// Example sorted array for testing
+	arr := []int{1, 3, 5, 7, 9, 11, 13, 15, 17, 19}
+
+	// Test binary search
+	target := 7
+	index := BinarySearch(arr, target)
+	fmt.Printf("BinarySearch: %d found at index %d\n", target, index)
+
+	// Test recursive binary search
+	recursiveIndex := BinarySearchRecursive(arr, target, 0, len(arr)-1)
+	fmt.Printf("BinarySearchRecursive: %d found at index %d\n", target, recursiveIndex)
+
+	// Test find insert position
+	insertTarget := 8
+	insertPos := FindInsertPosition(arr, insertTarget)
+	fmt.Printf("FindInsertPosition: %d should be inserted at index %d\n", insertTarget, insertPos)
+}
+
+// BinarySearch performs a standard binary search to find the target in the sorted array.
+// Returns the index of the target if found, or -1 if not found.
+func BinarySearch(arr []int, target int) int {
+	// TODO: Implement this function
+	
+	length := len(arr)
+	
+	if length == 0 {
+	    return -1
+	}
+	
+	start := 0
+	end := length - 1
+	mid := end / 2
+
+	if target == arr[start] {
+	    return start
+	}
+	
+	if target == arr[end] {
+	    return end
+	}
+		
+	for start != mid  {
+	    
+	    if target == arr[mid] {
+	        return mid
+	    }
+	    
+	    if target < arr[mid] {
+	        end = mid
+	        mid /= 2
+	    } else {
+	        start = mid
+	        mid = mid + ((end - mid) / 2)
+	    }
+	}
+	
+	return -1
+}
+
+// BinarySearchRecursive performs binary search using recursion.
+// Returns the index of the target if found, or -1 if not found.
+func BinarySearchRecursive(arr []int, target int, left int, right int) int {
+	// TODO: Implement this function
+	
+	length := len(arr)
+	if length == 0 {
+	    return -1
+	}
+	
+	if target == arr[left] {
+	    return left
+	}
+	
+	if target == arr[right] {
+	    return right
+	}
+	
+	mid := left + ((right - left) / 2)
+	
+	if target == arr[mid] {
+	    return mid
+	}
+	
+	if left == mid {
+	    return -1
+	}
+	
+	if(target < arr[mid]) {
+	    return BinarySearchRecursive(arr, target, left, mid)
+	} else {
+	    return BinarySearchRecursive(arr, target, mid, right)
+	}
+}
+
+// FindInsertPosition returns the index where the target should be inserted
+// to maintain the sorted order of the array.
+func FindInsertPosition(arr []int, target int) int {
+	// TODO: Implement this function
+	
+	length := len(arr)
+	start := 0
+	end := length - 1
+	mid := end / 2
+	
+	if length == 0 {
+	    return 0
+	}
+	
+	if target > arr[end] {
+	    return end + 1
+	}
+	
+	if target == arr[start] {
+	    return start
+	}
+	
+	if target == arr[end] {
+	    return end
+	}
+	
+	for start != mid  {
+
+	    if target == arr[mid] {
+	        return mid
+	    }
+	    
+	    if target < arr[mid] {
+	        end = mid
+	        mid /= 2
+	    } else {
+	        start = mid
+	        mid = mid + ((end - mid) / 2)
+	    }
+	}
+	
+	if mid == 0 {
+	    return 0
+	} else {
+	   if(target < arr[mid]) {
+	       return mid - 1
+	   } else {
+	       return mid + 1
+	   }
+	}
+}