2019-06-04剑指 power

class Solution:
    def Power(self, base, exponent):
        # write code here
        if base==0:return 0
        if exponent==0:return 1
        abs_e = abs(exponent)
        sign = abs_e // exponent #这里可能除0
        if sign == -1:
            return 1 / self.P(base,abs_e) # exponent #这里可能除0
        else:
            return self.P(base, abs_e)

    def P(self, base, abs_e):
        if abs_e==1:return base
        res=self.P(base,abs_e>>1)
        res*=res
        if(abs_e&1):res*=base
        return res