Heap implementation in Python

Author: OmkarPathak

Heap/Heap.py

@@ -0,0 +1,73 @@
+# Author: OMKAR PATHAK
+
+class BinaryHeap(object):
+    def __init__(self):
+        self.heap = [0]
+        self.currentSize = 0
+
+    def __repr__(self):
+        heap = self.heap[1:]
+        return ' '.join(str(i) for i in heap)
+
+    # for shifting the node up
+    def shiftUp(self, index):
+        while (index // 2) > 0:
+            if self.heap[index] < self.heap[index // 2]:     # (currentSize // 2) is the parent
+                temp = self.heap[index // 2]
+                self.heap[index // 2] = self.heap[index]
+                self.heap[index] = temp
+            index = index // 2
+
+    # to insert a node in the heap
+    def insert(self, key):
+        self.heap.append(key)
+        self.currentSize += 1
+        self.shiftUp(self.currentSize)
+
+    # for shifting down a node
+    def shiftDown(self, index):
+        while(index * 2) <= self.currentSize:
+            minimumChild = self.minChild(index)
+            if self.heap[index] > self.heap[minimumChild]:
+                temp = self.heap[index]
+                self.heap[index] = self.heap[minimumChild]
+                self.heap[minimumChild] = temp
+            index = minimumChild
+
+    # for finding the child with minimum value
+    def minChild(self,i):
+        if i * 2 + 1 > self.currentSize:
+            return i * 2
+        else:
+            if self.heap[i * 2] < self.heap[i * 2 + 1]:
+                return i * 2
+            else:
+                return i * 2 + 1
+
+    # for deleting a node from the heap and maintaining the heap property
+    def delete(self):
+        deletedNode = self.heap[1]
+        self.heap[1] = self.heap[self.currentSize]
+        self.currentSize -= 1
+        self.heap.pop()
+        self.shiftDown(1)
+        return deletedNode
+
+    # for building heap
+    def buildHeap(self, alist):
+        i = len(alist) // 2
+        self.currentSize = len(alist)
+        self.heap = [0] + alist[:]
+        while (i > 0):
+            self.shiftDown(i)
+            i = i - 1
+
+bh = BinaryHeap()
+bh.buildHeap([9,5,6,2,3])
+
+print('Deleted:', bh.delete())
+print('Deleted:', bh.delete())
+print('Deleted:', bh.delete())
+bh.insert(3)
+print('Deleted:', bh.delete())
+print(bh)