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

Master LeetCode problem 1343 (Number of Sub-arrays of Size K and Average Greater than or Equal to Threshold), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

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

Medium

Array Sliding Window

Problem Explanation

Explanation:

To solve this problem, we can use a sliding window approach. We will maintain a window of size k and compute the sum of elements within this window. If the average of this window is greater than or equal to the threshold, we increment a counter. We slide the window by removing the leftmost element and adding the rightmost element iteratively to check for all possible sub-arrays.

Algorithm:

Initialize variables sum to store the sum of the current window and count to store the count of sub-arrays meeting the criteria.
Iterate through the array from index 0 to n-1:
- Add the current element to sum.
- If the window size is greater than k, subtract the leftmost element from sum.
- If the window size is equal to k, check if the average of the window is greater than or equal to threshold. If true, increment count.
Return the final count.

Time Complexity:

The time complexity of this algorithm is O(n), where n is the number of elements in the input array.

Space Complexity:

The space complexity is O(1) as we are using only a constant amount of extra space.

Solution Code

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

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