def __init__(self):

self.max_heap = []

def peek(self) -> int:

# 大顶堆为空

if not self.max_heap:

return None

# 返回堆顶元素

return self.max_heap[0]

def push(self, val: int):

# 将新元素添加到堆的末尾

self.max_heap.append(val)

size = len(self.max_heap)

# 从新插入的元素节点开始，进行上移调整

self.__shift_up(size - 1)

def __shift_up(self, i: int):

while (i - 1) // 2 >= 0 and self.max_heap[i] > self.max_heap[(i - 1) // 2]:

self.max_heap[i], self.max_heap[(i - 1) // 2] = self.max_heap[(i - 1) // 2], self.max_heap[i]

i = (i - 1) // 2

def pop(self) -> int:

# 堆为空

if not self.max_heap:

raise IndexError("堆为空")

size = len(self.max_heap)

self.max_heap[0], self.max_heap[size - 1] = self.max_heap[size - 1], self.max_heap[0]

# 删除堆顶元素

val = self.max_heap.pop()

# 节点数减 1

size -= 1

self.__shift_down(0, size)

# 返回堆顶元素

return val

def __shift_down(self, i: int, n: int):

while 2 * i + 1 < n:

# 左右子节点编号

left, right = 2 * i + 1, 2 * i + 2

# 找出左右子节点中的较大值节点编号

if 2 * i + 2 >= n:

# 右子节点编号超出范围（只有左子节点

larger = left

else:

# 左子节点、右子节点都存在

if self.max_heap[left] >= self.max_heap[right]:

larger = left

else:

larger = right

# 将当前节点值与其较大的子节点进行比较

if self.max_heap[i] < self.max_heap[larger]:

# 如果当前节点值小于其较大的子节点，则将它们交换

self.max_heap[i], self.max_heap[larger] = self.max_heap[larger], self.max_heap[i]

i = larger

else:

# 如果当前节点值大于等于于其较大的子节点，此时结束

def maxHeapOperations(self):

max_heap = MaxHeap()

max_heap.push(3)

print(max_heap.peek())

max_heap.push(2)

print(max_heap.peek())

max_heap.push(4)

print(max_heap.peek())

max_heap.pop()