power_of_2.cpp

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#include <cassert>   
#include <cstdint>
#include <iostream>  
 
namespace bit_manipulation {
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
 
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;
}
int main() {
    test();  // run self-test implementations
    return 0;
}