快速幂

 1 #include<cstdio>
 2 #include<cstdlib>
 3 #include<iostream>
 4 using namespace std;
 5 int pow(int a, int b)
 6 {
 7     if(b == 0)
 8         return 1;
 9     else if(b == 1)
10         return a;
11     else
12     {
13         int c = pow(a, b / 2);
14         if((b % 2) == 0)
15             return c * c;
16         else
17             return c * c * a;
18     }
19 }
20 
21 int main()
22 {
23     int x, n;
24     cin >> x >> n;
25     cout << pow(x, n) << endl;
26     return 0;
27 }

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstdlib>
 4 using namespace std;
 5 
 6 long long Pow(long long x, long long n)
 7 {
 8     long long result;
 9     if(n == 0)
10         return 1;
11     else
12     {
13         while((n & 1) == 0)
14         {
15             n >> 1;
16             x *= x;
17         }
18     }
19     result = x;
20     n >> 1;
21     while(n != 0)
22     {
23         x *= x;
24         if((n & 1) != 0)
25             result *= x;
26         n >> 1;
27     }
28     return result;
29 }
30 
31 int main()
32 {
33     long long x, n;
34     cin >> x >> n;
35     cout << Pow(x, n) << endl;
36     return 0;
37 }