Add solution for Challenge 21 by ForcemCS

[ForcemCS]

Challenge 21 Solution

Submitted by: @ForcemCS
Challenge: Challenge 21

Description

This PR contains my solution for Challenge 21.

Changes

• Added solution file to challenge-21/submissions/ForcemCS/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 adds three public binary-search utility functions: BinarySearch (iterative), BinarySearchRecursive (recursive), and FindInsertPosition. Each function implements standard binary-search logic with appropriate edge-case handling for arrays of integers.

Changes

Cohort / File(s)	Summary
Binary Search Utilities challenge-21/submissions/ForcemCS/solution-template.go	Added three public functions for binary-search operations: BinarySearch (iterative, returns target index or -1), BinarySearchRecursive (recursive variant with left/right parameters), and FindInsertPosition (returns insertion index to maintain sorted order). Includes example usage in main function.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• Add solution for Challenge 21 by cckwes #849: Adds identical binary-search function implementations (BinarySearch, BinarySearchRecursive, FindInsertPosition) to a different submission directory for Challenge 21.
• Add solution for Challenge 21 by Be1chenok #586: Adds the same three binary-search utilities to challenge-21 solution files with equivalent logic and signatures.
• Add solution for Challenge 21 by rodney-b #707: Implements BinarySearch, BinarySearchRecursive, and FindInsertPosition functions in another Challenge 21 solution-template.go with matching functionality.

Poem

🐰 Hops through sorted arrays with binary grace,
Left and right pointers race,
Finding targets, positions too,
Recursive loops and loops that flew,
Search and sort—the rabbit's way! 🔍

🚥 Pre-merge checks | ✅ 2 | ❌ 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 (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: adding a solution for Challenge 21 by the user ForcemCS, which directly corresponds to the new Go solution file added in the changeset.
Description check	✅ Passed	The description is directly related to the changeset, explaining that it contains a Challenge 21 solution submission with details about the added file and testing performed.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (2)

challenge-21/submissions/ForcemCS/solution-template.go (2)

28-44: Remove leftover TODO comment and consider formatting cleanup.

The implementation is correct. However, the TODO comment on line 29 should be removed since the function is now implemented. Additionally, there are minor spacing inconsistencies (e.g., 0 , len(arr) -1 vs standard 0, len(arr)-1).

✨ Suggested cleanup

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

---

48-54: Remove leftover TODO comment.

The TODO comment on line 49 should be removed since the function is implemented.

---

ℹ️ Review info

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between a7ac764 and 3ccc676.

📒 Files selected for processing (1)

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

[coderabbitai]

⚠️ Potential issue | 🟠 Major

Bug: Use mid - 1 instead of right - 1 in the recursive call.

Line 61 passes right - 1 but should pass mid - 1 to correctly narrow the search space to the left half. This bug degrades performance from O(log n) to O(n) in worst cases and doesn't match the standard binary search algorithm.

🐛 Proposed fix

 	} else {
-	    return BinarySearchRecursive(arr, target, left , right -1 )
+	    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

	} else {
	return BinarySearchRecursive(arr, target, left , right -1 )
	} else {
	return BinarySearchRecursive(arr, target, left, mid-1)
	}