class ArrayStack:
def __init__(self, capacity=None):
"""
:param capacity: 栈的容积
"""
if capacity is None:
self.array = Array()
else:
self.array = Array(capacity)
def push(self, val):
"""
向数组的末尾添加一个元素
:param val:
:return:
"""
self.array.add_last(val)
def pop(self):
"""
弹出栈顶的元素，其实是栈顶的元素, 并删除
:return:
"""
return self.array.remove_last()
def peek(self):
"""
获取栈顶的元素，其实是数组的末尾元素
:return:
"""
return self.array.get_last()
def get_size(self):
return self.array.get_size()
def is_empty(self):
return self.array.is_empty()
def get_capacity(self):
return self.array.get_capacity()
def to_string(self):
res_str_stack = []
res_str_stack.append('Stack: [')
for i in range(0, self.array.get_size()):
val = self.array.get(i)
if isinstance(val, int):
val = str(val)
res_str_stack.append(val)
if i != self.array.get_size() - 1:
res_str_stack.append(',')
res_str_stack.append('] top')
return "".join(res_str_stack)
class MaxHeap:
def __init__(self, capacity=None, arr=None):
if arr is not None:
# 构建一个大根堆，通过heapify操作
self._heapify(arr)
return
if capacity is None:
self._data = Array()
else:
self._data = Array(capacity)
def get_size(self):
return self._data.get_size()
def is_empty(self):
return self._data.is_empty()
# 设置3个辅助函数, 通过给定节点的索引，计算当前节点的父亲索引、左孩子节点索引、右孩子节点索引
def _parent(self, index):
"""
返回完全二叉树的数组表示中，一个索引所表示的元素的父亲节点的索引
:param index:
:return:
"""
if index == 0:
raise (Exception, " index 0 doesn't have parent")
return (index - 1) // 2 # 整形部分
def _left_child(self, index):
return index * 2 + 1
def _right_child(self, index):
return index * 2 + 2
def add(self, e):
# 向堆中添加元素
self._data.add_last(e)
# 内部操作 Sift up(上浮，调整)
self._sift_up(self.get_size() - 1)
def _sift_up(self, index):
while index > 0 and self._data.get(
self._parent(index)) < self._data.get(index):
# index > 0 并且当前最新加入的节点值大于其父亲节点的值
self._data.swap(index, self._parent(index))
index = self._parent(index)
def find_max(self):
if self._data.is_empty():
raise (Exception, " can't find max when heap is empty!")
return self._data.get_first()
def _sift_down(self, index):
"""
获取元素，下沉操作，核心是确定当前的节点有没有左右孩子,时间复杂度是log(n)
:param index:
:return:
"""
while self._left_child(index) < self._data.get_size():
comp_child_index = self._left_child(index)
if comp_child_index + 1 < self._data.get_size() \
and self._data[comp_child_index + 1] > self._data[comp_child_index]:
comp_child_index = self._right_child(index)
if self._data[index] < self._data[comp_child_index]:
# 如果当前索引下值 < 子树节点中最大的值，则交换位置
self._data.swap(index, comp_child_index)
else:
break
index = comp_child_index
def extra_max(self):
ret = self.find_max()
self._data.swap(0, self._data.get_size() - 1)
self._data.remove_last()
# sift_down
self._sift_down(0) # 从根节点进行下浮
return ret
def replace(self, e):
"""
替换堆顶元素、并调整堆，下沉操作
:param e:
:return:
"""
ret = self.find_max()
self._data.set(0, e)
self._sift_down(0)
return ret
def _heapify(self, arr: Array):
"""
将一个数组转化为二叉大根堆
:param arr:
:return:
"""
self._data = arr
for i in range(self._parent(arr.get_size() - 1), -1, -1):
self._sift_down(i)