It's a bug, there's no question about it.

There is 100% a bug in the C RandomTests suite.

The bug is that it expects the input string to be modified in place, and it ignores the return value of your "correct" function.

There is no equivalent bug in C++, nor is there an equivalent bug in the C BasicTests suite.

This requirement is not stated in the problem, and is unique to one specific test suite in one specific language. It's a bug.

The workaround to meet this secret requirement is that you need to overwrite the input string with the result, before you return the result. That way, the broken RandomTests suite passes.

There is 100% a bug in the C RandomTests suite.

The bug is that it expects the input string to be modified in place, and it ignores the return value of your "correct" function.

There is no equivalent bug in C++, nor is there an equivalent bug in the C BasicTests suite.

This requirement is not stated in the problem, and is unique to one specific test suite in one specific language. It's a bug.

The workaround to meet this secret requirement is that you need to overwrite the input string with the result, before you return the result. That way, the broken RandomTests suite passes.

There is 100% a bug in the C RandomTests suite.

The bug is that it expects the input string to be modified in place, and it ignores the return value of your "correct" function.

There is no equivalent bug in C++, nor is there an equivalent bug in the C BasicTests suite.

This requirement is not stated in the problem, and is unique to one specific test suite in one specific language. It's a bug.

The workaround to meet this secret requirement is that you need to overwrite the input string with the result, before you return the result. That way, the broken RandomTests suite passes.