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leetcode-231-2的幂

作者:互联网

题目描述:

第一次提交:

class Solution:
    def isPowerOfTwo(self, n: int) -> bool:
        if n==0:return False
        if n==1:
            return True
        s = str(bin(n))[3:]
        for i in s:
            if i == '1':
                return False
        return True

优化:

class Solution:
    def isPowerOfTwo(self, n: int) -> bool:
        return n > 0 and bin(n).count("1") == 1

方法二:O(1)

class Solution:
    def isPowerOfTwo(self, n: int) -> bool:
        return n > 0 and n & (n - 1) == 0

方法三:O(logn)

class Solution:
    def isPowerOfTwo(self, n: int) -> bool:
        if n == 0: return False
        while n % 2 == 0:
            n //= 2
        return n == 1

 

标签:return,int,self,Solution,231,bool,isPowerOfTwo,leetcode
来源: https://www.cnblogs.com/oldby/p/11625041.html