Merge pull request #1 from s1s1ty/master

Heap code and test file added

Author: me-shaon

.gitignore

@@ -1 +1,2 @@
 **/__pycache__/*
+*.pyc

Data Structure/Heap/README.md

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+# Heap
+
+A **Heap** is a tree based data structure and it is a complete binary tree which satisfies the heap ordering property. The ordering can be one of two types:
+
+the **min-heap property:** the value of each node is greater than or equal to the value of its parent, with the minimum-value element at the root.
+
+the **max-heap property:** the value of each node is less than or equal to the value of its parent, with the maximum-value element at the root.
+
+![heap](max_heap_deletion_animation.gif)
+
+**Basic Operations:**
+
+Following are the basic operations supported by a list.
+
+* **Insertion** − Adds an element at the max heap.
+
+* **Deletion** − Deletes an element at the beginning of the heap.
+
+* **Display** − Displays the complete heap.
+
+* **Max** − Get the max element from the heap.
+
+
+#### Complexity Analysis
+- Space - O(n)
+- Search - O(n)
+- Insertion - O(1)
+- Delete - O(log n) (Deletion from beginning)
+- Peek - O(1)
+### More on this topic
+- https://en.wikipedia.org/wiki/Heap_(data_structure)
+- https://www.hackerearth.com/practice/data-structures/trees/heapspriority-queues/tutorial/
+- https://www.geeksforgeeks.org/binary-heap/

Data Structure/Heap/heap.py

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+"""MaxHeap implementation using python"""
+
+
+class MaxHeap(object):
+
+	def __init__(self, maxSize=None):
+		self.heap = []
+		self.HEAP_SIZE = maxSize
+
+	def _swap(self,i,j):
+		self.heap[i], self.heap[j] = self.heap[j], self.heap[i]
+
+	def _heapIsFull(self):
+		return (self.HEAP_SIZE != None and len(self.heap) >= self.HEAP_SIZE)
+
+	def insert(self, item):
+		if self._heapIsFull():
+			"Heap is full..."
+		else:
+			self.heap.append(item)
+			# adjust parent node item
+			self._bubbleUp(len(self.heap)-1)
+
+	def _bubbleUp(self, currentPosition):
+		if currentPosition >= 1: # no need to do bubbleUp for 1 element
+			index = currentPosition
+			parentIndex = (index-1)//2
+
+			if parentIndex >= 0 and self.heap[parentIndex] < self.heap[index]:
+				self._swap(parentIndex, index)
+				self._bubbleUp(parentIndex)
+			
+	def peek(self):
+		return self.heap[0] if self.heap else None
+
+	def pop(self):
+		element = self.peek()
+		if element:
+			self._swap(0, len(self.heap) - 1)
+			self.heap.pop()
+			self._bubbleDown(0)
+		return element
+
+	def _bubbleDown(self, index):
+		leftChildIndex = 2 * index + 1 
+		rightChildIndex = 2 * index + 2
+		largest = index
+		if len(self.heap) > leftChildIndex and self.heap[largest] < self.heap[leftChildIndex]:
+			largest = leftChildIndex
+		if len(self.heap) > rightChildIndex and self.heap[largest] < self.heap[rightChildIndex]:
+			largest = rightChildIndex
+		if largest!=index:
+			self._swap(index, largest)
+			self._bubbleDown(largest)

Data Structure/Heap/max_heap_deletion_animation.gif

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+import unittest
+from heap import MaxHeap
+
+class MaxHeapTestCase(unittest.TestCase):
+    """ Test for Heap.py"""
+    def test(self):
+        # test data 
+        ob = MaxHeap()
+        ob.insert(10)
+        ob.insert(5)
+        ob.insert(6)
+        ob.insert(3)
+        ob.insert(8)
+        ob.insert(20)
+        self.assertEqual(ob.peek(), 20, msg="Max Element is not matched")
+        ob.pop()
+        ob.pop()
+        self.assertEqual(ob.peek(), 8, msg="Max Element is not matched")
+        ob.pop()
+        self.assertEqual(ob.peek(), 6, msg="Max Element is not matched")
+        ob.pop()
+        ob.pop()
+        ob.pop()
+        self.assertEqual(ob.peek(), None, msg="Max Element is not matched")
+
+if __name__ == '__main__':
+    unittest.main()
+
+