Math - 50. Pow(x, n)
- 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]
思路：
题目是让实现幂次计算，做法是把幂次分解，分解到0，然后乘起来，比如
5^3 = 5^1 * 5^1 * 5^1 = (5^0 * 5^0 * 5^1) * (5^0 * 5^0 * 5^1)
代码：
go：
func myPow(x float64, n int) float64 {
if n > 0 {
return pow(x, n)
} else {
return 1.0 / pow(x, n)
}
}
func pow(x float64, n int) float64 {
if n == 0 {
return 1
}
y := pow(x, n/2)
if n % 2 == 0 {
return y * y
} else {
return y * y * x
}
}