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]
Solution in C++
class Solution {
public:
double myPow(double x, int n) {
if (!n || (x==1)) return 1;
double ret=1;
int iSign=(n>0)?1:-1;
if (fabs(n)>1) {
int nn=n/2;
int nMin=min(fabs(nn),fabs(nn-n))*iSign;
ret=myPow(x, nMin);
ret*=ret;
if (n%2==0) return ret;
n-= nMin*2;
}
if (n<0) ret /= x;
else ret *= x;
return ret;
}
};