50.cpp

// recursion.cpp
class Solution {
public:
    double myPow(double x, long long int n) {
        if (n == 0)
            return 1;
        if (n < 0) {
            x = 1 / x;
            n = -n;
        }
        return n % 2 == 0 ? myPow(x * x, n / 2) : x * myPow(x * x, n / 2);
    }
};