LeetCode "Super Pow"

A simple math on modular calculations.
Code below can be simplified of course.

class Solution {
    const int MOD = 1337;
    long long _pow(int a, int p)
    {
        if(p == 0) return 1;
        if(p == 1) return a;
        long long pr = _pow(a, p/2);
        long long r = p % 2 ? a : 1;
        return ((pr * pr) % MOD) * r %MOD;
    }
public:
    int superPow(int a, vector<int>& b) {
        
        int n = b.size();
        if(!n) return a % MOD;
        
        vector<long long> tmp(n);
        long long cb = a;
        for(int i = n - 1; i >= 0; i --)
        {
            tmp[i]  = _pow(cb, b[i]) % MOD;
            cb      = _pow(cb, 10) % MOD;
        }
        long long ret = 1;
        for(int i = 0; i < n; i ++)
        {
            ret = (ret * tmp[i]) % MOD;
        }
        return ret;
    }
};