LeetCode-in-Java

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

Medium

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 = [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.

Constraints:

• 1 <= arr.length <= 105
• 1 <= arr[i] <= 104
• 1 <= k <= arr.length
• 0 <= threshold <= 104

Solution

public class Solution {
    public int numOfSubarrays(int[] arr, int k, int threshold) {
        int sum = 0;
        for (int i = 0; i < k - 1; i++) {
            sum += arr[i];
        }
        int count = 0;
        for (int i = k - 1; i < arr.length; i++) {
            sum += arr[i];
            if (i - k >= 0) {
                sum -= arr[i - k];
            }
            if (sum / k >= threshold) {
                count++;
            }
        }
        return count;
    }
}

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