快速模幂

 1 #include <iostream>
 2   
 3 using namespace std;
 4 typedef long long ll;
 5 ll fun(ll a, ll b, ll mod)
 6 {
 7     ll ans=1%mod;
 8     while(b)
 9     {
10         if(b&1)
11         {
12             ans=(ans%mod*a%mod)%mod;
13 //            b--;
14         }
15         b>>=1;
16         a=(a*a)%mod;
17     }
18     return ans;
19 }
20 ll a,b,p;
21 int main()
22 {
23     cin>>a>>b>>p;
24     cout<<fun(a,b,p)<<endl;
25 //    cout << "Hello world!" << endl;
26     return 0;