power of n

Power of 2 

 return (n&(n-1)) ==0;

 n & (n-1)==0 is executed as n & ((n-1)==0) 

See https://en.wikipedia.org/wiki/OperatorsinCandC%2B%2B

class Solution {public:    bool isPowerOfTwo(int n) {        return ((n & (n- 1)) == 0 && (n > 0)) ? true : false;            }};

Power of 3

<span style="font-size:14px;">class Solution {public:    bool isPowerOfThree(int n) {                while ((n/3) != 0)        {            if ((n%3) != 0)            {                return false;            }            n = n / 3;        }        return (n == 1 ) ? true : false;                    }};</span>

Do it without any recursion or loop

https://leetcode.com/discuss/78532/summary-all-solutions-new-method-included-at-15-30pm-jan-8th

Power of 3

Rounds the specified uint 'value' up to the nearest value meeting the specified 'alignment'.  Only power of 2 alignments are supported 

return ((value + (alignment) - 1) & ~((alignment) - 1));

Determines if 'value' is at least aligned to the specified power-of-2 alignment.