feat: solve DaleStudy#289 with python

find-median-from-data-stream/EGON.py

@@ -0,0 +1,67 @@
+from heapq import heappush, heappop
+from unittest import TestCase, main
+
+
+class MedianFinder:
+    """
+    Runtime: 137 ms (Beats 56.16%)
+    Time Complexity:
+        1) addNum
+            - 최악의 경우 heappush + (heappop + heappush) + (heappop + heapppush) 가 발생할 수 있으므로 O(5 * log n)
+            > O(5 * log n) ~= O(log n)
+        2) findMedian
+            > heap의 루트 값을 가지고 사칙연산만 하므로 O(1)
+
+    Memory: 39.94 MB (Beats 5.85%)
+    Space Complexity: O(n)
+        - max_heap은 최대 n // 2 개 혹은 n // 2 + 1개의 원소를 가지므로 O(n / 2 + 1), upper bound
+        - min_heap은 최대 n // 2개의 원소를 가지므로 O(n / 2)
+        > O(n / 2 + 1) + O(n / 2) ~= O(n) + O(n) ~= O(n)
+    """
+
+    def __init__(self):
+        self.max_heap = []
+        self.min_heap = []
+
+    def addNum(self, num):
+        heappush(self.max_heap, -num)
+        if self.min_heap and (-self.max_heap[0] > self.min_heap[0]):
+            heappush(self.min_heap, -heappop(self.max_heap))
+
+        if len(self.max_heap) > len(self.min_heap) + 1:
+            heappush(self.min_heap, -heappop(self.max_heap))
+        elif len(self.max_heap) < len(self.min_heap):
+            heappush(self.max_heap, -heappop(self.min_heap))
+
+    def findMedian(self):
+        if self.max_heap and self.min_heap:
+            if len(self.max_heap) == len(self.min_heap):
+                return ((-self.max_heap[0]) + self.min_heap[0]) / 2
+            else:
+                return -self.max_heap[0]
+        elif self.min_heap and not self.max_heap:
+            return self.min_heap[0]
+        elif not self.min_heap and self.max_heap:
+            return -self.max_heap[0]
+        else:
+            return 0.0
+
+
+class _LeetCodeTestCases(TestCase):
+
+    def test_1(self):
+        medianFinder = MedianFinder()
+        medianFinder.addNum(-1)
+        self.assertEqual(medianFinder.findMedian(), -1.0)
+        medianFinder.addNum(-2)
+        self.assertEqual(medianFinder.findMedian(), -1.5)
+        medianFinder.addNum(-3)
+        self.assertEqual(medianFinder.findMedian(), -2.0)
+        medianFinder.addNum(-4)
+        self.assertEqual(medianFinder.findMedian(), -2.5)
+        medianFinder.addNum(-5)
+        self.assertEqual(medianFinder.findMedian(), -3.0)
+
+
+if __name__ == '__main__':
+    main()