Dumb and fast python solution


  • 0
    K

    Since there are only log(N) numbers that are powers of 4, and here we are limited by the 32(64) bits of basic integral type, just check them all:

    class Solution(object):
        def isPowerOfFour(self, num):
            """
            :type num: int
            :rtype: bool
            """
            if num <0 :
                return False
            if num==0:
                return False
            if num==1:
                return True
            powers4 = set([1,4,16,64,256,1024,4096,16384,65536,0x40000,0x100000,0x400000,0x1000000,0x4000000,0x10000000,0x40000000])
            return num in powers4

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