#### Power of 2

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```/**
* @file
* @brief [Find whether a given number is power of 2]
* (https://www.geeksforgeeks.org/program-to-find-whether-a-given-number-is-power-of-2/)
* implementation
*
* @details
* We are given a positive integer number. We need to check whether the number
* is power of 2 or not.
*
* A binary number consists of two digits. They are 0 & 1. Digit 1 is known as
* set bit in computer terms.
* Worst Case Time Complexity: O(1)
* Space complexity: O(1)
* @author [Prafful Gupta](https://github.com/EcstaticPG-25811)
*/

#include <cassert>   /// for assert
#include <iostream>  /// for IO operations

/**
* @namespace bit_manipulation
* @brief Bit manipulation algorithms
*/
namespace bit_manipulation {
/**
* @brief The main function implements check for power of 2
* @param n is the number who will be checked
* @returns either true or false
*/
bool isPowerOfTwo(std ::int64_t n) {  // int64_t is preferred over int so that
// no Overflow can be there.

return n > 0 && !(n & n - 1);  // If we subtract a power of 2 numbers by 1
// then all unset bits after the only set bit become set; and the set bit
// becomes unset.

// If a number n is a power of 2 then bitwise and of n-1 and n will be zero.
// The expression n&(n-1) will not work when n is 0.
// To handle this case also, our expression will become n& (!n&(n-1))
}
}  // namespace bit_manipulation

/**
* @brief Self-test implementations
* @returns void
*/
static void test() {
// n = 4 return true
assert(bit_manipulation::isPowerOfTwo(4) == true);
// n = 6 return false
assert(bit_manipulation::isPowerOfTwo(6) == false);
// n = 13 return false
assert(bit_manipulation::isPowerOfTwo(13) == false);
// n = 64 return true
assert(bit_manipulation::isPowerOfTwo(64) == true);
// n = 15 return false
assert(bit_manipulation::isPowerOfTwo(15) == false);
// n = 32 return true
assert(bit_manipulation::isPowerOfTwo(32) == true);
// n = 97 return false
assert(bit_manipulation::isPowerOfTwo(97) == false);
// n = 1024 return true
assert(bit_manipulation::isPowerOfTwo(1024) == true);
std::cout << "All test cases successfully passed!" << std::endl;
}
/**
* @brief Main function
* @returns 0 on exit
*/
int main() {
test();  // run self-test implementations
return 0;
}
```  