LeetCode 643. Maximum Average Subarray I

class Solution {
public:
    double findMaxAverage(vector<int>& nums, int k) {
        int sum = accumulate(nums.begin(), nums.begin() + k, 0);
        int maxSum = sum;
        for (int i = k; i < nums.size(); ++i) {
            sum += (nums[i] - nums[i - k]);
            maxSum = max(maxSum, sum);
        }
        return 1.0 * maxSum / k;
    }
};