643. 子数组最大平均数 I

 

 代码一思路：遍历nums，每一趟遍历k个元素求和s前，将s清零，不过酱超时。

class Solution(object):
    def findMaxAverage(self, nums, k):
        """
        :type nums: List[int]
        :type k: int
        :rtype: float
        """
        res = 0
        if len(nums)<=k:
            for i in range(len(nums)):
                res += nums[i]
            return res/float(k)
        i, j = 0, k - 1
        while j < len(nums):
            s = 0
            for index in range(i, j + 1):
                s += nums[index]
            if res <= s:
                res = s
            i += 1
            j += 1
        return res / float(k)

代码二思路：遍历nums，每一趟遍历k个元素求和s时，用“去头加尾”的方法。

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