Question
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]
Difficulty:Medium
Category:Math, Binary-Search
Analyze
使用分治法,解决求解一半的情况: double half = power(x, n/2);
Solution
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;
else
return x * half * half;
}
};