作业帮笔试第一题,快速幂加求逆元
快速幂代码就不写了,直接调用库函数
#求逆元 def get_(a, b): if b == 0: return 1, 0 else: k = a // b remainder = a % b x1, y1 = get_(b, remainder) x, y = y1, x1 - k * y1 return x, y def powersum(x,n): x = x % mod if x==1: return n%mod y, _ = get_(x - 1, mod) #(求(x-1)逆元) a = (((pow(x, n + 1, mod) - x)) * y) % mod #等比数列求和公式 return a mod = 998244353 x = 998244357 n =100000000000000000000000000 a = powersum(x,n) print(a)