#223 · #1343 · Number of Sub-arrays of Size K and Average Greater than or Equal to Threshold(大小为 K 且平均值大于等于阈值的子数组数目)

Given an array of integers arr and two integers k and threshold, return the number of sub-arrays of size k whose average is greater than or equal to threshold. Constraints: 1 <= arr.length <= 10^5, 1 <= arr[i] <= 10^4, 1 <= k <= arr.length, 0 <= threshold <= 10^4.