- Pow(x, n)
Implement pow(x, n), which calculates x
raised to the power n
(i.e., x^n
).
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 = 1/2^2 = 1/4 = 0.25
Constraints:
-100.0 < x < 100.0
-2^31 <= n <= 2^31-1
n
is an integer.- Either
x
is not zero orn > 0
. -10^4 <= x^n <= 10^4
Idea
text
* 调库函数Math.pow(x,n)
* 暴力乘法
* 分治递归,一分为二
JavaScript Solution
javascript
/**
* @param {number} x
* @param {number} n
* @return {number}
*/
var myPow = function(x, n) {
if( !n ){
return 1
}
if( n < 0 ){
return 1/myPow(x,-n)
}
if( n%2 ){
return x*myPow(x,n-1)
}
return myPow(x*x, n/2 );
};