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.

class Solution {
public:
    double findMaxAverage(vector<int>& nums, int k) {
        double res = -1e5 - 1;
        int sum = 0;
        for(int i = 0; i < nums.size(); i++) {
            sum += nums[i];
            if(i >= k) sum -= nums[i-k];
            if(i + 1 >= k) res = max(res, 1. * sum / k);
        }
        return res;
    }
};