231. Power of Two

Given an integer, write a function to determine if it is a power of two.

Credits:
Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

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注意 处理负数的情况。

class Solution {public:    bool isPowerOfTwo(int n) {        // if(n<=0) return 0;        return (n>0) && (n&(n-1))==0;    }};