feat: solve 1087. Brace Expansion with unit testing

[mathusanm6]

closes #86

[Copilot]

Pull Request Overview

This PR adds a complete solution for LeetCode problem 1087 "Brace Expansion" with implementations in both Python and C++, including comprehensive unit tests and documentation. It also includes minor code style improvements in an existing test file.

• Implementation of brace expansion algorithm using backtracking approach in both languages
• Addition of unit test suites with multiple test cases covering basic expansion, no braces, and complex scenarios
• Update to repository documentation to reflect the new solution count

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
problems/calculate_amount_paid_in_taxes/calculate_amount_paid_in_taxes_test.cc	Minor style improvements to use const reference and consistent spacing
problems/brace_expansion/config.yml	Configuration file defining problem metadata and complexity analysis
problems/brace_expansion/brace_expansion_test.py	Python unit tests with parametrized test cases
problems/brace_expansion/brace_expansion_test.cc	C++ unit tests using Google Test framework
problems/brace_expansion/brace_expansion.py	Python implementation using recursive backtracking with regex
problems/brace_expansion/brace_expansion.h	C++ header file declaring the main function
problems/brace_expansion/brace_expansion.cc	C++ implementation using iterative approach with regex
README.md	Updated solution counts and added new backtracking section

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