Maximum Average Subarray I.py

'''
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 <= k <= n <= 30,000.
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
        """
        max_sum = float('-inf')
        tmp = 0
        for i in xrange(len(nums)):
            tmp += nums[i]
            if i - k >= 0:
                tmp -= nums[i-k]
            if i - k >= -1:
                max_sum = max(max_sum, tmp)
                
        return 1.0 * max_sum / k