643. Maximum Average Subarray I

1. Question:

643. Maximum Average Subarray I

url https://leetcode.com/problems/maximum-average-subarray-i/

Given an array consisting of n integers, find the contiguous subarray of given length k that has the maximum average value. And you need to output the maximum average value.

Example 1:

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

Note:

1. 1 <= k <= n <= 30,000.
2. Elements of the given array will be in the range [-10,000, 10,000].

2. Solution:

class Solution(object):
    def findMaxAverage(self, nums, k):
        """
        :type nums: List[int]
        :type k: int
        :rtype: float
        """
        size = len(nums)
        if k == 1:
            return max(nums)

        left_sum = 0
        right_sum = nums[0]
        for i in range(1, k):
            right_sum = right_sum + nums[i]

        max_sum = right_sum
        left_index = 0
        right_index = k
        while right_index < size:
            left_sum += nums[left_index]
            right_sum += nums[right_index]
            tmp = right_sum - left_sum
            if max_sum < tmp:
                max_sum = tmp
            left_index += 1
            right_index += 1
        return max_sum / k

3. Complexity Analysis

Time Complexity : O(N)

Space Complexity: O(1)