面试题 16. 数值的整数次方

输入: 2.00000, 10
输出: 1024.00000

输入: 2.10000, 3
输出: 9.26100

输入: 2.00000, -2
输出: 0.25000
解释: 2-2 = 1/22 = 1/4 = 0.25

class Solution:
    def myPow(self, x: float, n: int) -> float:
        if n == 0:
            return 1
        if n == 1:
            return x
        if n == -1:
            return 1 / x
        half = self.myPow(x, n // 2)
        return half * half * self.myPow(x, n % 2)

class Solution {
    public double myPow(double x, int n) {
        if (n == 0) return 1;
        if (n == 1) return x;
        if (n == -1) return 1 / x;
        double half = myPow(x, n / 2);
        return half * half * myPow(x, n % 2);
    }
}

/**
 * @param {number} x
 * @param {number} n
 * @return {number}
 */
var myPow = function (x, n) {
  let r = 1;
  let tmp = x;
  let tag = 0;
  if (n < 0) {
    tag = 1;
    n = -n;
  }
  while (n) {
    if (n & 1) {
      r *= tmp;
    }
    tmp *= tmp;
    n >>>= 1;
  }
  return tag ? 1 / r : r;
};

func myPow(x float64, n int) float64 {
    p := abs(n)
    res := 1.0
    for p != 0 {
        if p&1 == 1 {
            res *= x
        }
        x *= x
        p = p >>1
    }
    if n < 0 {
        return 1/res
    }
    return res
}

func abs(x int) int {
    if x > 0 {
        return x
    }
    return -x
}