快速幂实现次方

# 实现a的b次幂
def power(a, b):
    if a==0:
        return -1
    if b==0 and a>0:
        return 1
    temp = 1
    while b:
        if b&1:
            temp *= a
        a *=a
        b = b>>1
    return temp

print(power(3,3))