Add solution for Challenge 21 by alimkinpark

[alimkinpark]

Challenge 21 Solution

Submitted by: @alimkinpark
Challenge: Challenge 21

Description

This PR contains my solution for Challenge 21.

Changes

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

Testing

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

Thank you for reviewing my submission! 🚀

[coderabbitai]

Walkthrough

A new Go solution file is added containing three binary search implementations (iterative, recursive, and insertion-position finding) along with a main() test harness that demonstrates their usage on sample data.

Changes

Cohort / File(s)	Summary
Binary Search Implementation challenge-21/submissions/alimkinpark/solution-template.go	Introduces BinarySearch() for iterative binary search, BinarySearchRecursive() for recursive implementation, and FindInsertPosition() to locate insertion indices; includes a main() function demonstrating all three functions with example values.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• Add solution for Challenge 21 by rodney-b #707: Adds the same three exported binary search functions (BinarySearch, BinarySearchRecursive, FindInsertPosition) in challenge-21 submissions at the code level.
• Add solution for Challenge 21 by ForcemCS #1456: Implements identical binary-search function signatures and logic in challenge-21 solution-template.go.
• Add solution for Challenge 21 by Johrespi #655: Adds matching function implementations with a test harness in challenge-21 submissions directory.

Poem

🐰 Hops through sorted arrays with glee,
Binary bounds grow wild and free,
Left and right dance, searching well,
Insert positions? Rabbit can tell!
Recursion bounces, left then right,
Challenge twenty-one shines bright! ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 75.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: adding a solution for Challenge 21 by a specific contributor.
Description check	✅ Passed	The description is directly related to the changeset, clearly identifying the challenge being solved and the file being added.
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.

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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 (2.11.4)

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

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[coderabbitai]

Actionable comments posted: 1

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 7b4003b7-5be3-47b2-827f-aba043b6eabb

📥 Commits

Reviewing files that changed from the base of the PR and between bf844ae and b91e5b2.

📒 Files selected for processing (1)

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

[coderabbitai]

⚠️ Potential issue | 🟠 Major | ⚡ Quick win

Use mid to shrink recursive bounds.

At Line 65 and Line 67, the recursion updates with left + 1 / right - 1 instead of mid + 1 / mid - 1. This breaks binary-search narrowing, increases recursion depth, and can cause stack pressure on large inputs.

Suggested fix

-	if arr[mid] < target {
-	    return BinarySearchRecursive(arr, target, left + 1, right)
-	} else {
-	    return BinarySearchRecursive(arr, target, left, right - 1)
-	}
+	if arr[mid] < target {
+	    return BinarySearchRecursive(arr, target, mid+1, right)
+	}
+	return BinarySearchRecursive(arr, target, left, mid-1)

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

	if arr[mid] < target {
	return BinarySearchRecursive(arr, target, left + 1, right)
	} else {
	return BinarySearchRecursive(arr, target, left, right - 1)
	if arr[mid] < target {
	return BinarySearchRecursive(arr, target, mid+1, right)
	}
	return BinarySearchRecursive(arr, target, left, mid-1)

[github-actions]

⚠️ Auto-merge failed

Could not automatically merge this PR: Resource not accessible by integration

A maintainer will need to merge manually.

[github-actions]

⚠️ Auto-merge failed

Could not automatically merge this PR: Resource not accessible by integration

A maintainer will need to merge manually.

[github-actions]

👋 Action needed for auto-merge

This PR cannot be auto-merged because "Allow edits from maintainers" is enabled. This is a GitHub limitation with automated workflows.

To fix: Please uncheck "Allow edits from maintainers" in the PR sidebar (under the reviewers section), and the PR will be auto-merged in the next cycle.

Alternatively, a maintainer can merge this manually.