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

Tags : array, slidingwindow, leetcode, cpp, medium

Problem Statement - link #

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.

Examples #

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 #

Solutions #

class Solution {
public:
    int numOfSubarrays(vector<int>& arr, int k, int threshold) {
      int sum = 0, res = 0;
      for(int i=0; i<k-1; i++) sum+=arr[i];
      for(int i=k-1; i<arr.size(); i++){
        sum += arr[i];
        int avg = sum/k;
        if(avg >= threshold) res++;
        sum -= arr[i-k+1];
      }
      
      return res;
    }
};