---
title: 'LeetCode 643. Maximum Average Subarray I'
disqus: hackmd
---

# LeetCode 643. Maximum Average Subarray I

## Description

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

Input: nums = [1,12,-5,-6,50,3], k = 4
Output: 12.75000
Explanation: Maximum average is (12 - 5 - 6 + 50) / 4 = 51 / 4 = 12.75

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

## Constraints

n == nums.length
1 <= k <= n <= 10^5^
-10^4^ <= nums[i] <= 10^4^

## Answer

此題可直接用一個for做疊加，算到k-1項後就可以加入max的判斷，接下來的計算除了跌加之外還要減掉num[i-k]項，如此才能算是k個項相加，最後return時再取平均即可。

//2022_03_13
double findMaxAverage(int* nums, int numsSize, int k){
    double ans = 0, max = *nums;
    for(int i = 1; i<numsSize; i++){
        nums[i] += nums[i-1];
        if(i >= k-1){
            if(i == k-1){max = nums[i];}
            else{
                ans = nums[i] - nums[i-k];
                max = max > ans ? max : ans;
            }
        }
    }
    return max/k;
}

## Link
https://leetcode.com/problems/maximum-average-subarray-i/
###### tags: `Leetcode`