leetcode 643. 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].

   class Solution(object):
       def findMaxAverage(self, nums, k):
           """
           :type nums: List[int]
           :type k: int
           :rtype: float
           """
           # just iterate
           # init: s
           s = sum(nums[:k])
           ans = float(s)/k
           for i in xrange(k, len(nums)):
               s = s+nums[i]-nums[i-k]
               ans = max(ans, float(s)/k)
           return ans