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

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

Description

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:

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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:

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

Hints/Notes

  • 2024/10/04
  • sliding window
  • No solution from 0x3F

Solution

Language: C++

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