How do I implement a max heap in Python?

How do I implement a max heap in Python?

To implement a max heap in Python, you can use a list to represent the heap. Would you like a code example?

Yes, please provide a code example.

Here's a simple implementation:

class MaxHeap:
    def __init__(self):
        self.heap = []

    def insert(self, val):
        self.heap.append(val)
        self._heapify_up(len(self.heap) - 1)

    def _heapify_up(self, index):
        parent = (index - 1) // 2
        if index > 0 and self.heap[index] > self.heap[parent]:
            self.heap[index], self.heap[parent] = self.heap[parent], self.heap[index]
            self._heapify_up(parent)

    def extract_max(self):
        if not self.heap:
            return None
        max_val = self.heap[0]
        self.heap[0] = self.heap.pop()
        self._heapify_down(0)
        return max_val

    def _heapify_down(self, index):
        largest = index
        left = 2 * index + 1
        right = 2 * index + 2
        if left < len(self.heap) and self.heap[left] > self.heap[largest]:
            largest = left
        if right < len(self.heap) and self.heap[right] > self.heap[largest]:
            largest = right
        if largest != index:
            self.heap[index], self.heap[largest] = self.heap[largest], self.heap[index]
            self._heapify_down(largest)

Would you like to know how to use this class?

Yes, how can I use this MaxHeap class?

You can use the MaxHeap class like this:

heap = MaxHeap()
heap.insert(10)
heap.insert(20)
heap.insert(5)
print(heap.extract_max())  # Output: 20