LeetCode 50. Pow(x, n)

Description

https://leetcode.com/problems/longest-increasing-subsequence/

Implement pow(xn), 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]

Explanation

break into cases

Python Solution

class Solution:
    def myPow(self, x: float, n: int) -> float:

        if n == 0:
            return 1

        if n < 0:
            return 1/self.myPow(x, -n)

        elif n % 2 == 0:
            return self.myPow(x * x, n//2)

        elif n % 2 == 1:
            return x * self.myPow(x * x, n//2)
  • Time complexity: ~log(N)
  • Space complexity: ~1

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