Here's the question reformatted to be more concise and direct:

Reverse String

Create code to reverse a string. For example, "hello" should become "olleh". Return an empty string if the input is empty, and null if the input is null.

Examples:

Input: str = "hello" Output: "olleh" Input: str = "Hi There" Output: "erehT iH" Input: str = "" Output: "" Input: str = null Output: null
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