231.是否为2的平方根 IsPowerOfTwo

Total Accepted: 3596 Total Submissions: 11779

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.

[思路]

如果是power of two, 则2进制表达中,有且仅有一个1. 可以通过移位来数1的个数, 这里用了一个巧妙的办法, 即判断 N & (N-1) 是否为0.

[CODE]

public class Solution {  
    public boolean IsPowerOfTwo(int n) {  
       return n > 0 && ((n & (n - 1)) == 0 );  
    }  
}