https://leetcode.com/problems/super-pow/#/description
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.
a ^ 123456 % 1337 = (a ^ 123450 % 1337) * (a ^ 6 % 1337) % 1337 = ((a ^ 12345) ^ 10 % 1337) * (a ^ 6 % 1337) % 1337
mod(a, b, k) = (a ^ b) % k
public class Solution { public int superPow(int a, int[] b) { return superPow(a, b, b.length, 1337); } private int superPow(int a, int[] b, int n, int k) { if (n == 1) { return mod(a, b[0], k); } return mod(superPow(a, b, n - 1, k), 10, k) * mod(a, b[n - 1], k) % k; } private int mod(int a, int b, int k) { a %= k; int res = 1; for (int i = 0; i < b; i++) { res = res * a % k; } return res; } }