Add solution for Challenge 21 by WHFF521

[WHFF521]

Challenge 21 Solution

Submitted by: @WHFF521
Challenge: Challenge 21

Description

This PR contains my solution for Challenge 21.

Changes

• Added solution file to challenge-21/submissions/WHFF521/solution-template.go

Testing

• Solution passes all test cases
• Code follows Go best practices

Thank you for reviewing my submission! 🚀

[coderabbitai]

Walkthrough

Adds three exported Go binary-search utilities for sorted integer slices and a main function that demonstrates their returned indices.

Changes

Binary Search Utilities

Layer / File(s)	Summary
Binary search implementations challenge-21/submissions/WHFF521/solution-template.go	Adds iterative and recursive searches returning an index or -1, plus insertion-position calculation that preserves sorted order.
Example execution challenge-21/submissions/WHFF521/solution-template.go	Runs each helper against an example sorted slice and prints the results.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• RezaSi/go-interview-practice#586: Adds the same Challenge 21 functions with matching behavior.
• RezaSi/go-interview-practice#655: Implements the same three exported binary-search utilities and demo.
• RezaSi/go-interview-practice#1877: Adds equivalent Challenge 21 Go binary-search helpers.

Poem

A rabbit hops through sorted hay,
Finds each carrot on the way.
Recursive paws search left and right,
New carrots fit in order just right.
Three tools printed—what a delight! 🐇

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly matches the main change: adding a Challenge 21 solution submission.
Description check	✅ Passed	The description is directly related to the submitted Challenge 21 solution and its added file.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 golangci-lint (2.12.2)

level=error msg="[linters_context] typechecking error: pattern ./...: directory prefix . does not contain main module or its selected dependencies"

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[coderabbitai]

🧹 Nitpick comments (3)

challenge-21/submissions/WHFF521/solution-template.go (3)

29-41: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Remove TODO and apply standard Go formatting.

The implementation is functionally correct. You can optionally clean up the lingering TODO comment and apply standard gofmt styling (such as adding spaces around operators) for better readability.

♻️ Proposed refactor

-	// TODO: Implement this function
 	left := 0
-	right := len(arr)-1
-	for left<=right{
-	    mid := left + (right - left)/2
-	    if arr[mid] == target {
-	        return mid
-	    }else if arr[mid] < target{
-	        left = mid+1
-	    }else {
-	        right = mid-1
-	    }
-	}
+	right := len(arr) - 1
+	for left <= right {
+		mid := left + (right-left)/2
+		if arr[mid] == target {
+			return mid
+		} else if arr[mid] < target {
+			left = mid + 1
+		} else {
+			right = mid - 1
+		}
+	}

---

48-60: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Remove unreachable code and format.

The return -1 at the end of the function is unreachable because the preceding if/else if/else block covers all conditions and returns in every branch. This can be cleaned up alongside the lingering TODO comment and standard formatting.

♻️ Proposed refactor

-	// TODO: Implement this function
-	if left > right{
-	    return -1
-	}
-	mid := left + (right - left)/2
-	if arr[mid] == target{
-	    return mid
-	}else if arr[mid] < target{
-	    return BinarySearchRecursive(arr,target,mid+1,right)
-	}else {
-	    return BinarySearchRecursive(arr,target,left,mid-1)
-	}
-	return -1
+	if left > right {
+		return -1
+	}
+	mid := left + (right-left)/2
+	if arr[mid] == target {
+		return mid
+	} else if arr[mid] < target {
+		return BinarySearchRecursive(arr, target, mid+1, right)
+	}
+	return BinarySearchRecursive(arr, target, left, mid-1)

---

66-79: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Remove redundant variable assignment and format.

The mid variable is initialized outside the loop but is immediately overwritten on the first iteration before being used. The initial calculation can be safely removed.

♻️ Proposed refactor

-	// TODO: Implement this function
 	left := 0
-	right := len(arr)-1
-	mid := left + (right - left)/2
-	for left<=right{
-	    mid = left + (right - left)/2
-	    if arr[mid] == target {
-	        return mid
-	    }else if arr[mid] < target{
-	        left = mid+1
-	    }else {
-	        right = mid-1
-	    }
-	}
+	right := len(arr) - 1
+	for left <= right {
+		mid := left + (right-left)/2
+		if arr[mid] == target {
+			return mid
+		} else if arr[mid] < target {
+			left = mid + 1
+		} else {
+			right = mid - 1
+		}
+	}

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 8b209eed-d6c7-4828-a24d-04588e496f1c

📥 Commits

Reviewing files that changed from the base of the PR and between 8522a72 and 621915f.

📒 Files selected for processing (1)

• challenge-21/submissions/WHFF521/solution-template.go

[github-actions]

🎉 Auto-merged!

This PR was automatically merged after 2 days with all checks passing.

Thank you for your contribution, @WHFF521!

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