fix: Replace VLAs with std::vector in C++ Huffman Code

[tsainez]

This pull request replaces the non-standard C-style Variable Length Arrays (VLAs) in c++/huffmanCodes.cpp with standard std::vector<int>.

The author of the code noted that the previous array initialization (int arr[n];) caused segmentation faults. This is because dynamically allocating variable-length arrays on the stack is not standard C++ and can lead to stack overflows or compiler issues depending on the extensions supported by the compiler used.

Changes made:

• Replaced int arr[n] and int bits[n] with std::vector<int> arr(n) and std::vector<int> bits(n).
• Updated function signatures huffmanEncode, traverse, and printBits to use const std::vector<int>& where applicable to avoid unnecessary copies while providing the array data to helper functions.
• Removed outdated and incorrect array-size logic (sizeof(arr) / sizeof(arr[0])).
• Changed int j to size_t j in the loop condition in main to address signed/unsigned comparison warnings against .size().

Tested locally by providing an input set and verifying output encoded binaries remain correct.

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PR created automatically by Jules for task 3341179921368451821 started by @tsainez

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