372. Super Pow

Problem:

Your 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.

Example 1:

Input: a = 2, b = [3]
Output: 8

Example 2:

Input: a = 2, b = [1,0]
Output: 1024

思路：

Solution (C++):

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

性能：

Runtime: 12 ms  Memory Usage: 6.9 MB

思路：

Solution (C++):

性能：

Runtime: ms  Memory Usage: MB