Add solution for Challenge 21 by yz4230

[yz4230]

Challenge 21 Solution

Submitted by: @yz4230
Challenge: Challenge 21

Description

This PR contains my solution for Challenge 21.

Changes

• Added solution file to challenge-21/submissions/yz4230/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 submission file implementing three binary search utility functions: an iterative binary search, a recursive variant, and a function to find insertion position in a sorted array. The file includes a main function demonstrating usage of these utilities.

Changes

Cohort / File(s)	Change Summary
Binary Search Utilities challenge-21/submissions/yz4230/solution-template.go	New file with iterative BinarySearch, recursive BinarySearchRecursive, and FindInsertPosition functions, plus a sample main demonstrating their usage.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

• All three functions implement standard binary search algorithms with straightforward logic
• Single file addition with self-contained functionality
• Consistent pattern throughout (no heterogeneous or complex logic density)

Possibly related PRs

• RezaSi/go-interview-practice#626: Adds the same three binary search functions with equivalent implementations in a different submission file.
• RezaSi/go-interview-practice#714: Adds identical binary search utility functions in separate challenge-21 submission files.
• RezaSi/go-interview-practice#707: Implements the same three binary search functions with equivalent logic and demo main in a different submission.

Pre-merge checks

❌ 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%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: adding a solution file for Challenge 21 by a specific author, which matches the PR objectives and file additions.
Description check	✅ Passed	The description is directly related to the changeset, clearly explaining that it adds a Challenge 21 solution and specifying the file path where the solution was added.

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (2)

challenge-21/submissions/yz4230/solution-template.go (2)

7-24: Consider adding more comprehensive test cases.

The main function demonstrates basic usage well, but for a practice submission, consider testing additional scenarios:

• Target not found (for both search functions)
• Empty array
• Single element array
• Target at boundaries (first/last element)
• Target outside array range (smaller/larger than all elements)

---

64-78: Significant code duplication with BinarySearch.

Lines 67-75 duplicate the search logic from BinarySearch (lines 31-39). The only difference is the final return value (left vs -1).

Consider refactoring to eliminate duplication, for example by having BinarySearch use FindInsertPosition internally:

func BinarySearch(arr []int, target int) int {
    pos := FindInsertPosition(arr, target)
    if pos < len(arr) && arr[pos] == target {
        return pos
    }
    return -1
}

Or by extracting the common binary search logic into a helper function.

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 9b711a4 and 95fc7aa.

📒 Files selected for processing (1)

• challenge-21/submissions/yz4230/solution-template.go (1 hunks)

🔇 Additional comments (1)

challenge-21/submissions/yz4230/solution-template.go (1)

46-60: LGTM! Correct recursive implementation.

The recursive binary search correctly implements a closed interval [left, right] approach with proper base case handling and boundary adjustments.

[coderabbitai]

⚠️ Potential issue | 🟡 Minor

Inconsistent interval convention with recursive variant.

The iterative BinarySearch uses a half-open interval [left, right) (initialized with right := len(arr)), while BinarySearchRecursive uses a closed interval [left, right] (called with len(arr)-1). Both implementations are correct individually, but the inconsistency can confuse maintainers.

Consider standardizing on one convention across both functions for better code consistency.

🤖 Prompt for AI Agents

challenge-21/submissions/yz4230/solution-template.go lines 28-42: the iterative
BinarySearch uses a half-open interval [left,right) (right := len(arr)) while
the recursive variant uses a closed interval [left,right] (invoked with
len(arr)-1), causing inconsistency; pick one convention and make both functions
match — either change the iterative function to use closed interval (initialize
right := len(arr)-1, adjust loop condition to left <= right and update pointers
accordingly) or change the recursive variant to use half-open bounds (accept
right as len(arr) and treat right as exclusive in the recursion), and update all
comparisons/indices and base cases to follow the chosen convention consistently.