一、题目

643. Maximum Average Subarray I

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 = 4
Output: 12.75000
Explanation: Maximum average is (12 - 5 - 6 + 50) / 4 = 51 / 4 = 12.75
Example 2:

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

Constraints:

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

二、题解

利用滑动窗口的性质解题

class Solution {
public:
    double findMaxAverage(vector<int>& nums, int k) {
        int n = nums.size();
        double res = INT_MIN;
        double tmp = 0;
        for(int i = k - 1;i < n;i++){
            if(i == k - 1){
                int count = k;
                while(count--) tmp += nums[i-count];
                res = max(tmp,res);
            }
            else{
                tmp -= nums[i - k];
                tmp += nums[i];
                res = max(tmp,res);
            }
        }
        return res / k;
    }
};