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]
注意n=-2147482648（-2^31）的情况
class Solution {
public:
double myPow(double x, int n) {
if(n==0)
return 1;
else if(n<0)
return 1.0/myPow(x,-(n+1))*(1.0/x);
double y=myPow(x,n/2);
return y*y*(n%2==0 ? 1 : x);
}
};