動機

大概抓到sliding window的模式了

Problem

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 = 4Output: 12.75000Explanation: Maximum average is (12 - 5 - 6 + 50) / 4 = 51 / 4 = 12.75

Example 2:

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

 

Constraints:

  • n == nums.length
  • 1 <= k <= n <= 105
  • -104 <= nums[i] <= 104

Sol

a = 0
win_cnt = sum(s[a:b-1])
for b in range(b-1,len(s)):
    win_cnt += s[b]

    f()

    win_cnt -= s[a]
    a += 1

class Solution:
    def findMaxAverage(self, nums: List[int], k: int) -> float:
        a, cnt = 0,0
        
        ret = sum(nums[:k])/k
        cnt = sum(nums[:k-1])*1.0
        for b in range(k-1,len(nums)):
            cnt += nums[b]
            ret = max(ret, cnt/k)
            
            cnt -= nums[a]
            a+=1
        return ret