In C++ why is a binary search function almost always more efficient than a linear search function?

In C++ Declare a Character Pointer and allocate a dynamic array of 22 characters.

Write a function in c called recursively_reverse_string() that accepts a pointer to a string as a parameter, and any other parameters you see fit, recursively reverses the string, and returns a pointer to the reversed string. For example, the reversed string of input “string” is “gnirts”.