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Problem Definition:

Write one line C function to find whether a no is power of two.

Solution:

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 become unset.

For example for 4 ( 100) and 16(10000), we get following after subtracting 1

So, if a number n is a power of 2 then bitwise & of n and n-1 will be zero. We can say n is a power of 2 or not based on value of n&(n-1).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)).

Code:

/* Function to check if x is power of 2*/bool isPowerOfTwo (int x){  /* First x in the below expression is for the case when x is 0 */  return x && (!(x&(x-1)));}

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