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 = [1,1,1,1,1], k = 1, threshold = 0
Output: 5
Example 3:
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.
Example 4:
Input: arr = [7,7,7,7,7,7,7], k = 7, threshold = 7
Output: 1
Example 5:
Input: arr = [4,4,4,4], k = 4, threshold = 1
Output: 1
Constraints:
1 <= arr.length <= 10^5
1 <= arr[i] <= 10^4
1 <= k <= arr.length
0 <= threshold <= 10^4
class Solution:
    def numOfSubarrays(self, arr: List[int], k: int, threshold: int) -> int:
        ans = 0
        total = 0
        threshold = k*threshold
        if len(arr) < k:
            return 0
        else:
            #check the first k numbers
            for i in range(k):
                total += arr[i]
            if total >= threshold:
                ans += 1    
            
            #slide window to the right 1
            i = k
            while i < len(arr):                
                total += arr[i] - arr[i-k]
                if total >= threshold:
                    ans += 1
                i += 1
            return ans
class Solution:
    def numOfSubarrays(self, arr: List[int], k: int, threshold: int) -> int:
        ans = 0
        total = 0
        threshold = k*threshold
        if len(arr) < k:
            return 0
        else:
            #check the first k numbers
            for i in range(k):
                total += arr[i]
            if total >= threshold:
                ans += 1    
            
            #slide window to the right 1
            i = k
            while i < len(arr):                
                total += arr[i] - arr[i-k]
                if total >= threshold:
                    ans += 1
                i += 1
            return ans