Day 43: Implement MaxHeap using recursion for bubbleUp and bubbleDown

Author: thatguyintech

day43/README.md

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+Let's rewrite the heap I did in day 38 and make it better.
+And also make it a max heap.
+
+## Code
+
+[Python](./maxHeap.py)
+
+## Follow-up

day43/maxHeap.py

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+from collections import deque
+
+class MaxHeap:
+    def __init__(self, arr=[]):
+        self.data = deque()
+        self.size = 0
+        if len(arr) > 0:
+            self.size = len(arr)
+            self.__heapify(arr)
+
+    def getMax(self):
+        if self.size > 0:
+            ret = self.data.popleft()
+            self.size -= 1
+            self.data.appendleft(self.data.pop())
+            self.__bubbleDown(0)
+            return ret
+
+    def peek(self):
+        if self.size > 0:
+            return self.data[0]
+
+    def push(self, val):
+        self.data.append(val)
+        self.size += 1
+        self.__bubbleUp(self.size-1)
+
+    def isEmpty(self):
+        return self.size == 0
+
+    def __heapify(self, arr):
+        self.data = deque(arr)
+        for i in xrange(len(arr)-1, -1, -1):
+            self.__bubbleDown(i)
+
+    def __bubbleDown(self, index):
+        left = self.__left(index)
+        right = self.__right(index)
+
+        larger = index
+
+        if left < self.size and self.data[index] < self.data[left]:
+            larger = left
+
+        if right < self.size and self.data[left] < self.data[right]:
+            larger = right
+
+        if larger != index:
+            self.data[larger], self.data[index] = self.data[index], self.data[larger]
+            self.__bubbleDown(larger)
+
+    def __bubbleUp(self, index):
+        p = self.__parent(index)
+
+        if p >= 0 and self.data[index] > self.data[p]:
+            self.data[index], self.data[p] = self.data[p], self.data[index]
+            self.__bubbleUp(p)
+
+    def __parent(self, i):
+        return i/2
+
+    def __left(self, i):
+        return 2*i + 1
+
+    def __right(self, i):
+        return 2*i + 2
+
+def testPush():
+    h = MaxHeap()
+    h.push(2)
+    assert h.data[0] == 2
+
+    h.push(3)
+    assert h.data[0] == 3
+
+    h.push(1)
+    assert h.data[0] == 3
+
+    h.push(5)
+    assert h.data[0] == 5
+
+    h.push(-1)
+    assert h.data[0] == 5
+
+def testGetMax():
+    heap = MaxHeap([2, 5, 20])
+    assert heap.getMax() == 20
+    assert heap.getMax() == 5
+
+    heap1 = MaxHeap([1, 2, 3, 4, 5])
+    assert heap1.getMax() == 5
+    assert heap1.getMax() == 4
+
+    heap2 = MaxHeap([5, 4, 3, 2, 1])
+    assert heap2.getMax() == 5
+    assert heap2.getMax() == 4
+
+    heap3 = MaxHeap([2, 5, 3, 7, -1])
+    assert heap3.getMax() == 7
+    assert heap3.getMax() == 5
+
+def testPeek():
+    heap = MaxHeap([2, 5, 20])
+    assert heap.peek() == 20
+    assert heap.peek() == 20
+
+    heap1 = MaxHeap([1, 2, 3, 4, 5])
+    assert heap1.peek() == 5
+    assert heap1.peek() == 5
+
+    heap2 = MaxHeap([5, 4, 3, 2, 1])
+    assert heap2.peek() == 5
+    assert heap2.peek() == 5
+
+    heap3 = MaxHeap([2, 5, 3, 7, -1])
+    assert heap3.peek() == 7
+    assert heap3.peek() == 7
+
+def testSize():
+    heap = MaxHeap()
+    assert heap.size == 0
+
+    heap2 = MaxHeap([1])
+    assert heap2.size == 1
+
+    heap3 = MaxHeap([1, 2, 3, 4])
+    assert heap3.size == 4
+
+def testIsEmpty():
+    heap = MaxHeap()
+    assert heap.isEmpty()
+
+    heap2 = MaxHeap([1])
+    assert not heap2.isEmpty()
+
+    heap3 = MaxHeap([1, 2, 3])
+    assert not heap3.isEmpty()
+
+def testEverything():
+    assert True
+
+def tests():
+    testPush()
+    testGetMax()
+    testPeek()
+    testSize()
+    testIsEmpty()
+    testEverything()
+
+if __name__ == "__main__":
+    tests()