50. Pow(x, n)

Description

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]

Answer

package main

import (
    "fmt"
)

func myPow(x float64, n int) float64 {
    if n == 0 {
        return 1
    }

    if n%2 == 0 {
        return myPow(x*x, n/2)
    } else {
        if n > 0 {
            return x * myPow(x, n-1)
        } else {
            return 1 / x * myPow(x, n+1)
        }
    }

    /*
    //时间复杂度超时
    
    var result float64 = 1

    if x == 1.00000 {
        return 1.00000
    }
    temp := int(math.Abs(float64(n)))
    for i := 1; i <= temp; i++ {
        result = result * x
    }
    if n < 0 {
        result = 1 / result
    }
    return result*/
}

func main() {
    fmt.Println(myPow(2.00000, -2))
}