A的B次幂

Description

给出两个正整数A和B

请输出A的B次幂

结果可能很大，请对1000000007求模

Input

A和B，两个整数均不大于10^18

Output

A的B次幂对1000000007求模

Sample Input 1

2 2

Sample Output 1

Sample Input 2

2 10

Sample Output 2

1024

快速幂：其实我也没搞明白。emmmmmmm等我搞明白了再说吧。献上代码！

 1 #include<iostream>
 2 using namespace std;
 3 long long cu(long long a, long long b) {
 4     long long s = 1;
 5     while(b > 0) {
 6         if(b%2 == 1) {
 7             s = s % 1000000007;
 8             a = a % 1000000007;
 9             s = s * a;
10         }
11         a = a % 1000000007;
12         a = a * a;
13         b = b / 2;
14     }
15     return s % 1000000007;
16 }
17 int main()
18 {
19     long long a, b;
20     cin >> a >> b;
21     cout << cu(a, b);
22 }