leetcode342. Power of Four
2016-07-02 16:39
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Given an integer (signed 32 bits), write a function to check whether it is a power of 4.
Example:
Given num = 16, return true. Given num = 5, return false.
Follow up: Could you solve it without loops/recursion?
x&(x-1)==0 ->x为2的幂
4的幂的1在奇数位上
Example:
Given num = 16, return true. Given num = 5, return false.
Follow up: Could you solve it without loops/recursion?
x&(x-1)==0 ->x为2的幂
4的幂的1在奇数位上
class Solution(object): def isPowerOfFour(self, num): """ :type num: int :rtype: bool """ return num>0 and (num &(num-1))==0 and (num & 0x55555555) == num
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