Question

Min heap class implementation in Python.

Implement a min-using an array. Your min-heap class will have one private attribute, an array of integers. Implement the following methods for the min-heap class You may not use the built-in min function. init - Constructor makes an empty heap str - Prints the heap out in any way you want for debugging only) makenull(self) - Makes the heap empty insert(self,x) - Insert element x into the heap parent(self,i) - Returns the index of the parent of the element at index i (p=(i-1)/2) left(self,i) - Returns the index of the left child of the element at index i (I=(i+1)*2-1 right(self,i) - Returns the index of the right child of the element at indexi (r=(i+1)*2) swap(self, a,b) - Swaps elements at indexes a and b upheap(self,i) - Upheaps starting at index i downheap(self,i) - Downheaps starting at index i inorder(self,i) - Returns a string of the tree inorder starting at index i (put spaces after each value) preorder(self,i) - Returns a string of the tree in preorder starting at index i (put spaces after each value) postorder(self,i) - Returns a string of the tree in postorder starting at index i (put spaces after each value) min(self) - returns the smallest value in heap. deletemin(self)-deletes smallest number in heap sort(self) - Print out the values, one per line, in sorted order. This command destroys the heap. A test system is provided that will test your implementation. An example execution is provided below.

Answer 1

class BinaryHeap:
    def __init__(self):
        self.items = []
 
    def size(self):
        return len(self.items)
 
    def parent(self, i):
        return (i - 1)//2
 
    def left(self, i):
        return 2*i + 1
 
    def right(self, i):
        return 2*i + 2
 
    def get(self, i):
        return self.items[i]
 
    def get_max(self):
        if self.size() == 0:
            return None
        return self.items[0]
 
    def extract_max(self):
        if self.size() == 0:
            return None
        largest = self.get_max()
        self.items[0] = self.items[-1]
        del self.items[-1]
        self.max_heapify(0)
        return largest
 
    def max_heapify(self, i):
        l = self.left(i)
        r = self.right(i)
        if (l <= self.size() - 1 and self.get(l) > self.get(i)):
            largest = l
        else:
            largest = i
        if (r <= self.size() - 1 and self.get(r) > self.get(largest)):
            largest = r
        if (largest != i):
            self.swap(largest, i)
            self.max_heapify(largest)
 
    def swap(self, i, j):
        self.items[i], self.items[j] = self.items[j], self.items[i]
 
    def insert(self, key):
        index = self.size()
        self.items.append(key)
 
        while (index != 0):
            p = self.parent(index)
            if self.get(p) < self.get(index):
                self.swap(p, index)
            index = p
 
 
bheap = BinaryHeap()
 
print('Menu')
print('insert <data>')
print('max get')
print('max extract')
print('quit')
 
while True:
    do = input('What would you like to do? ').split()
 
    operation = do[0].strip().lower()
    if operation == 'insert':
        data = int(do[1])
        bheap.insert(data)
    elif operation == 'max':
        suboperation = do[1].strip().lower()
        if suboperation == 'get':
            print('Maximum value: {}'.format(bheap.get_max()))
        elif suboperation == 'extract':
            print('Maximum value removed: {}'.format(bheap.extract_max()))
 
    elif operation == 'quit':
        break