使用对数lg直接估算所求位数，每次乘以2^60大大加快速度（不够60再乘以更小的）9*2^60为10,376,293,541,461,622,784刚好不会超ull范围(18,446,744,073,709,551,616)#include<iostream>#include<cstdio>#include<cmath>usingnamespacestd;typedefunsignedlonglongull;