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]
class Solution {
/* x = 2.00000, n = -2147483648
expected = 0 */
public:
double myPow(double x, int n) {
if(n == 0) return 1;
if(fabs(x) < epsilon) return 0;
bool neg = (n < 0);
unsigned int un = fabs(n);
double res = 1;
while(un > 0){
if(un&1) res *= x;
un >>= 1;
x *= x;
} if(neg) return 1/res;
return res;
}
private:
const double epsilon = 1e-9;
};