1343. Number of Sub-arrays of Size K and Average Greater than or Equal to Threshold

Given an array of integers arr and two integers k and threshold.

Return the number of sub-arrays of size k and average greater than or equal to threshold.

 

Example 1:

Input: arr = [2,2,2,2,5,5,5,8], k = 3, threshold = 4
Output: 3
Explanation: Sub-arrays [2,5,5],[5,5,5] and [5,5,8] have averages 4, 5 and 6 respectively. All other sub-arrays of size 3 have averages less than 4 (the threshold).

Example 2:

Input: arr = [1,1,1,1,1], k = 1, threshold = 0
Output: 5

Example 3:

Input: arr = [11,13,17,23,29,31,7,5,2,3], k = 3, threshold = 5
Output: 6
Explanation: The first 6 sub-arrays of size 3 have averages greater than 5. Note that averages are not integers.

Example 4:

Input: arr = [7,7,7,7,7,7,7], k = 7, threshold = 7
Output: 1

Example 5:

Input: arr = [4,4,4,4], k = 4, threshold = 1
Output: 1

 

Constraints:

  • 1 <= arr.length <= 10^5
  • 1 <= arr[i] <= 10^4
  • 1 <= k <= arr.length
  • 0 <= threshold <= 10^4

Solution

class Solution
{
public:
    int numOfSubarrays(vector<int> &arr, int k, int threshold)
    {
        int st = 0, end = k - 1;
        int curr = 0;
        int cnt = k, ans = 0;
        for (int i = st; i <= end; i++)
        {
            curr += arr[i];
        }
        if (curr / k >= threshold)
        {
            ans++;
        }

        while (end < arr.size())
        {

            end++;
            if (end < arr.size())
            {
                curr += arr[end];
                curr -= arr[st];
                st++;

                if ((curr / k) >= threshold)
                {

                    ans++;
                }
            }
        }
        return ans;
    }
};