[leetcode] 643. Maximum Average Subarray I _ Algorithm Problem Solve for python

1. Problem

643. Maximum Average Subarray I

You are given an integer array nums consisting of n elements, and an integer k.

Find a contiguous subarray whose length is equal to k that has the maximum average value and return this value. Any answer with a calculation error less than 10-5 will be accepted.

Example 1:

Input: nums = [1,12,-5,-6,50,3], k = 4
Output: 12.75000
Explanation: Maximum average is (12 - 5 - 6 + 50) / 4 = 51 / 4 = 12.75

Example 2:

Input: nums = [5], k = 1
Output: 5.00000

Constraints:

• n == nums.length
• 1 <= k <= n <= 10^5
• -10^4 <= nums[i] <= 10^4

2. Solution

I solved this problem like this.

• Complexity
  • Time complexity : O(N)
  • Space complexity : O(N)
• Step
  • Get first k sum & append sum_list
  • When we calculate next sum, add right new value and subtract left value
  • Find max value on sum_list

class Solution:
    def findMaxAverage(self, nums: List[int], k: int) -> float:
        sum_list = [sum(nums[:k])]
        for idx in range(k, len(nums)):
            sum_list.append(sum_list[-1] - nums[idx - k] + nums[idx])
        
        return round(max(sum_list)/k, 5)