Add solution for Challenge 21 by dquang0504

[dquang0504]

Challenge 21 Solution

Submitted by: @dquang0504
Challenge: Challenge 21

Description

This PR contains my solution for Challenge 21.

Changes

• Added solution file to challenge-21/submissions/dquang0504/solution-template.go

Testing

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

Thank you for reviewing my submission! 🚀

[coderabbitai]

Walkthrough

Adds a new Go file implementing three binary search utility functions: an iterative version, a recursive variant, and an insertion position finder that returns -1 when targets are not found. Includes a main function demonstrating usage with a sample sorted array.

Changes

Cohort / File(s)	Summary
Binary Search Implementation challenge-21/submissions/dquang0504/solution-template.go	New file with three exported functions: BinarySearch() (iterative), BinarySearchRecursive() (recursive), and FindInsertPosition() (lower_bound insertion index). All not-found cases return -1. Includes demo main function with test outputs.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• Add solution for Challenge 21 by manik23 #1071: Adds the same three binary-search functions (BinarySearch, BinarySearchRecursive, FindInsertPosition) to a different challenge-21 submission file.
• Add solution for Challenge 21 by Johrespi #655: Adds identical exported functions with the same signatures and implementation pattern in a different challenge-21 submission.
• Add solution for Challenge 21 by BroQi #852: Adds the same binary-search utility functions to a different challenge-21 submission file.

🚥 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 clearly identifies that this PR adds a solution for Challenge 21 submitted by dquang0504, which directly matches the main purpose of the changeset.
Description check	✅ Passed	The description is directly related to the changeset, explaining that it contains a solution for Challenge 21 with details about the file added and testing status.

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