题目内容 (Markdown)

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 = [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.

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#include <iostream>
#include <vector>

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