题目

pow(x,n)

算法

* 直接模拟

* 直接模拟优化

* 迭代

代码

* 直接模拟

class Solution {

public:

    double myPow(double x, int n) {

        if (n < 0) return 1 / power(x, -n);

        return power(x, n);

    }

    double power(double x, int n) {

        if (n == 0) return 1;

        double half = power(x, n / 2);

        if (n % 2 == 0) return half * half;

        return x * half * half;

    }

};

* 直接模拟优化

class Solution {

public:

    double myPow(double x, int n) {

        if (n == 0) return 1;

        double half = myPow(x, n / 2);

        if (n % 2 == 0) return half * half;

        else if (n > 0) return half * half * x;

        else return half * half / x;

    }

};

* 迭代

class Solution {

public:

    double myPow(double x, int n) {

        double res = 1.0;

        for (int i = n; i != 0; i /= 2) {

            if (i % 2 != 0) res *= x;

            x *= x;

        }

        return n < 0 ? 1 / res : res;

    }

};