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);
}
};
