Super Pow问题及解法

问题描述：

our task is to calculate ab mod 1337 where a is a positive integer and b is an extremely large positive integer given in the form of an array.

示例:

a = 2b = [3]Result: 8

a = 2b = [1,0]Result: 1024

问题分析：

利用欧拉准则和递归的方法，即可求得答案。

这里简单说一下欧拉准则：ab % k = (a%k)(b%k)%k

过程详见代码：

class Solution {public:    const int base = 1337;int powmod(int a, int k){a %= base;int res = 1;for (int i = 0; i < k; i++){res = (res * a) % base;}return res;}int superPow(int a, vector<int>& b) {if (b.empty()) return 1;int last = b.back();b.pop_back();return powmod(superPow(a, b), 10) * powmod(a, last) % base;}};