leetcode#50 Pow(x,n)

Implement pow(x, n), which calculates x raised to the power n (xn).

Example 1:

Input: 2.00000, 10
Output: 1024.00000

Example 2:

Input: 2.10000, 3
Output: 9.26100

Example 3:

Input: 2.00000, -2
Output: 0.25000
Explanation: 2-2 = 1/22 = 1/4 = 0.25

Note:

• -100.0 < x < 100.0
• n is a 32-bit signed integer, within the range [−231, 231 − 1]

这道题没有规定复杂度，但是直接计算会超时。本题是数据结构的示例之一。

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;
    }
};