算法——求幂

求幂

二的幂次方都有一个特点，这些数字的二进制数都只会出现一个1，跟着几个0。

而四的幂次方则相似，不过它们的二进制数中0只会出现偶数次、而不是奇数次。

# power_exponent.py 求幂
from math import pow

class Solution:
    def is_power_of_two(self, n: int) -> bool:
        if n <= 0:
            return False
        if bin(n)[2:].count('1') == 1:
            return True
        return False

    def is_power_of_four(self, n: int) -> bool:
        if n <= 0:
            return False
        s = bin(n)[2:]
        if s.count('1') == 1 and s.count('0') % 2 == 0:
            return True
        return False

def test():
    solution = Solution()
    l = [int(pow(2, i)) for i in range(10)]
    #l = [i for i in range(100)]
    for i in l:
        print(i, bin(i))
        print('is_power_of_two: ', solution.is_power_of_two(i))
        print('is_power_of_four: ', solution.is_power_of_four(i))

if __name__ == '__main__':
    test()