FZU-1759 Super A^B mod C---欧拉降幂&指数循环节

题目链接：

https://cn.vjudge.net/problem/FZU-1759

题目大意：

求A^B%C

解题思路：

注意，这里long long需要用%I64读入，不能用%lld

 #include<iostream>
 #include<cstdio>
 #include<cmath>
 #include<cstring>
 using namespace std;
 typedef long long ll;
 const int maxn = 2e6 + ;
 int euler_phi(int n)//求单个
 {
     int m = (int)sqrt(n + 0.5);
     int ans = n;
     for(int i = ; i <= m; i++)if(n % i == )
     {
         ans = ans / i * (i - );
         while(n % i == )n /= i;
     }
     if(n > )ans = ans / n * (n - );
     return ans;
 }
 ll mul(ll a, ll b, ll m)
 //求a*b%m
 {
     ll ans = ;
     a %= m;
     while(b)
     {
         if(b & )ans = (ans + a) % m;
         b /= ;
         a = (a + a) % m;
     }
     return ans;
 }
 ll pow(ll a, ll b, ll m)
 {
     ll ans = ;
     a %= m;
     while(b)
     {
         if(b & )ans = mul(a, ans, m);
         b /= ;
         a = mul(a, a, m);
     }
     ans %= m;
     return ans;
 }
 ll super_pow(ll a, char b[], ll c)
 {
     ll t = euler_phi(c), n = strlen(b), tot = ;
     for(int i = ; i < n; i++)
     {
         tot = tot *  + b[i] - '';
         tot %= t;
     }
     tot += t;
     return pow(a, tot, c);
 }
 char b[maxn];
 int main()
 {
     ll a, c;
     while(~scanf("%I64d%s%I64d", &a, b, &c))
     {
         printf("%I64d\n", super_pow(a, b, c));
     }
     return ;
 }