Create number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.py

Author: kamyu104

Python/number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.py

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+# Time:  O(n)
+# Space: O(1)
+
+import itertools
+
+
+class Solution(object):
+    def numOfSubarrays(self, arr, k, threshold):
+        """
+        :type arr: List[int]
+        :type k: int
+        :type threshold: int
+        :rtype: int
+        """
+        result, curr = 0, sum(itertools.islice(arr, 0, k-1))
+        for i in xrange(k-1, len(arr)):
+            curr += arr[i]-(arr[i-k] if i-k >= 0 else 0)
+            result += int(curr >= threshold*k)
+        return result
+    
+
+# Time:  O(n)
+# Space: O(n)
+class Solution2(object):
+    def numOfSubarrays(self, arr, k, threshold):
+        """
+        :type arr: List[int]
+        :type k: int
+        :type threshold: int
+        :rtype: int
+        """
+        accu = [0]
+        for x in arr:
+            accu.append(accu[-1]+x)
+        result = 0
+        for i in xrange(len(accu)-k):
+            if accu[i+k]-accu[i] >= threshold*k:
+                result += 1
+        return result