LeetCode50. Pow(x, n)

一、题目

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

Example 1:

Input: x = 2.00000, n = 10
Output: 1024.00000
Example 2:

Input: x = 2.10000, n = 3
Output: 9.26100
Example 3:

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

Constraints:

-100.0 < x < 100.0
-231 <= n <= 231-1
n is an integer.
Either x is not zero or n > 0.
-104 <= xn <= 104

二、题解

class Solution {
public:
    double quickMul(double x,long long N){
        double res = 1.0;
        while(N > 0){
            if((N & 1) == 1){
                res *= x;
            }
            x *= x;
            N = N >> 1;
        }
        return res;
    }
    double myPow(double x, int n) {
        long long N = n;
        return N > 0 ? quickMul(x,N) : 1.0 / quickMul(x,-N);
    }
};