Heap

Python

class Heap:

    def __init__(self):
        self.lst = []

    def get_left_child_index(self, index):
        return (2 * index) + 1

    def get_right_child_index(self, index):
        return (2 * index) + 2

    def get_parent_index(self, index):
        return (index - 1) // 2

    def has_left_child(self, index):
        return self.get_left_child_index(index) < len(self.lst)

    def has_right_child(self, index):
        return self.get_right_child_index(index) < len(self.lst)

    def has_parent(self, index):
        return self.get_parent_index(index) >= 0

    def swap(self, first, second):
        self.lst[first], self.lst[second] = self.lst[second], self.lst[first]

    def peek(self):
        if not self.lst:
            return None
        return self.lst[0]

    def poll(self):
        if not self.lst:
            return None
        item = self.lst[0]
        self.swap(0, -1)
        self.lst.pop()
        self.heapify_down()
        return item

    def add(self, data):
        self.lst.append(data)
        self.heapify_up()

    def heapify_up(self):
        index = len(self.lst) - 1
        while self.has_parent(index):
            parent_index = self.get_parent_index(index)
            if self.lst[parent_index] > self.lst[index]:
                self.swap(parent_index, index)
            index = parent_index

    def heapify_down(self):
        index = 0
        while self.has_left_child(index):
            smaller_index = self.get_left_child_index(index)
            if self.has_right_child(index) and self.lst[self.get_right_child_index(index)] < self.lst[smaller_index]:
                smaller_index = self.get_right_child_index(index)
            if self.lst[index] < self.lst[smaller_index]:
                break
            self.swap(index, smaller_index)
            index = smaller_index

h = Heap()
h.add(20)
h.add(17)
h.add(15)
h.add(10)

print(h.poll())
print(h.poll())
print(h.poll())
print(h.poll())

Second Tab