Given a positive integer, write a function to find if it is a power of two or not.
Naive solution
In naive solution we just keep dividing the number by two
unless the number becomes 1 and every time we do so we
check that remainder after division is always 0. Otherwise
the number can’t be a power of two.
Bitwise solution
Powers of two in binary form always have just one bit.
The only exception is with a signed integer (e.g. an 8-bit
signed integer with a value of -128 looks like: 10000000)
1: 0001
2: 0010
4: 0100
8: 1000
So after checking that the number is greater than zero, we can use a bitwise hack to test that one and only one bit is set.
number & (number - 1)
For example for number 8 that operations will look like:
1000
- 0001
----
0111
1000
& 0111
----
0000