myPow.cpp

class Solution {
public:
    unordered_map<int, double> mp;

    double myPow(double x, int n) {

        int64_t m = (int64_t)n;

        if (n < 0) {
            x = 1 / x;
            m = -m;
        }

        mp[0] = 1;
        mp[1] = x;

        return recursivePow(x, m);
    }

    double recursivePow(double x, int64_t n) {

        auto itr = mp.find(n);
        if(itr != mp.end()) {
            return itr->second;
        }

        auto left = n / 2;
        auto right = n - left;

        auto left_result = recursivePow(x, left);
        auto right_result = recursivePow(x, right);
        
        auto temp = left_result * right_result;
        mp[n] = temp;

        return temp;
    }
};