# A Python program to demonstrate common binary heap operations
# Import the heap functions from python library
from heapq import heappush, heappop, heapify
# heappop - pop and return the smallest element from heap
# heappush - push the value item onto the heap, maintaining
# heap invarient
# heapify - transform list into heap, in place, in linear time
# A class for Min Heap
class MinHeap:
# Constructor to initialize a heap
def __init__(self):
self.heap = []
def parent(self, i):
return (i-1)/2
# Inserts a new key 'k'
def insertKey(self, k):
heappush(self.heap, k)
# Decrease value of key at index 'i' to new_val
# It is assumed that new_val is smaller than heap[i]
def decreaseKey(self, i, new_val):
self.heap[i] = new_val
while(i != 0 and self.heap[self.parent(i)] > self.heap[i]):
# Swap heap[i] with heap[parent(i)]
self.heap[i] , self.heap[self.parent(i)] = (
self.heap[self.parent(i)], self.heap[i])
# Method to remove minium element from min heap
def extractMin(self):
return heappop(self.heap)
# This functon deletes key at index i. It first reduces
# value to minus infinite and then calls extractMin()
def deleteKey(self, i):
self.decreaseKey(i, float("-inf"))
self.extractMin()
# Get the minimum element from the heap
def getMin(self):
return self.heap[0]
# Driver pgoratm to test above function
heapObj = MinHeap()
heapObj.insertKey(3)
heapObj.insertKey(2)
heapObj.deleteKey(1)
heapObj.insertKey(15)
heapObj.insertKey(5)
heapObj.insertKey(4)
heapObj.insertKey(45)
print heapObj.extractMin(),
print heapObj.getMin(),
heapObj.decreaseKey(2, 1)
print heapObj.getMin()
# This code is contributed by Nikhil Kumar Singh(nickzuck_007)