Python编程实现双链表，栈，队列及二叉树的方法示例

class Node(object):  def __init__(self, value=None):    self._prev = None    self.data = value    self._next = None  def __str__(self):    return "Node(%s)"%self.dataclass DoubleLinkedList(object):  def __init__(self):    self._head = Node()  def insert(self, value):    element = Node(value)    element._next = self._head    self._head._prev = element    self._head = element  def search(self, value):    if not self._head._next:      raise ValueError("the linked list is empty")    temp = self._head    while temp.data != value:      temp = temp._next    return temp  def delete(self, value):    element = self.search(value)    if not element:      raise ValueError('delete error: the value not found')    element._prev._next = element._next    element._next._prev = element._prev    return element.data  def __str__(self):    values = []    temp = self._head    while temp and temp.data:      values.append(temp.data)      temp = temp._next    return "DoubleLinkedList(%s)"%values

class Stack(object):  def __init__(self):    self._top = 0    self._stack = []  def put(self, data):    self._stack.insert(self._top, data)    self._top += 1  def pop(self):    if self.isEmpty():      raise ValueError('stack 为空')    self._top -= 1    data = self._stack[self._top]    return data  def isEmpty(self):    if self._top == 0:      return True    else:      return False  def __str__(self):    return "Stack(%s)"%self._stack

class Queue(object):  def __init__(self, max_size=float('inf')):    self._max_size = max_size    self._top = 0    self._tail = 0    self._queue = []  def put(self, value):    if self.isFull():      raise ValueError("the queue is full")    self._queue.insert(self._tail, value)    self._tail += 1  def pop(self):    if self.isEmpty():      raise ValueError("the queue is empty")    data = self._queue.pop(self._top)    self._top += 1    return data  def isEmpty(self):    if self._top == self._tail:      return True    else:      return False  def isFull(self):    if self._tail == self._max_size:      return True    else:      return False  def __str__(self):    return "Queue(%s)"%self._queue

class Node:  def __init__(self,item):    self.item = item    self.child1 = None    self.child2 = Noneclass Tree:  def __init__(self):    self.root = None  def add(self, item):    node = Node(item)    if self.root is None:      self.root = node    else:      q = [self.root]      while True:        pop_node = q.pop(0)        if pop_node.child1 is None:          pop_node.child1 = node          return        elif pop_node.child2 is None:          pop_node.child2 = node          return        else:          q.append(pop_node.child1)          q.append(pop_node.child2)  def traverse(self): # 层次遍历    if self.root is None:      return None    q = [self.root]    res = [self.root.item]    while q != []:      pop_node = q.pop(0)      if pop_node.child1 is not None:        q.append(pop_node.child1)        res.append(pop_node.child1.item)      if pop_node.child2 is not None:        q.append(pop_node.child2)        res.append(pop_node.child2.item)    return res  def preorder(self,root): # 先序遍历    if root is None:      return []    result = [root.item]    left_item = self.preorder(root.child1)    right_item = self.preorder(root.child2)    return result + left_item + right_item  def inorder(self,root): # 中序序遍历    if root is None:      return []    result = [root.item]    left_item = self.inorder(root.child1)    right_item = self.inorder(root.child2)    return left_item + result + right_item  def postorder(self,root): # 后序遍历    if root is None:      return []    result = [root.item]    left_item = self.postorder(root.child1)    right_item = self.postorder(root.child2)    return left_item + right_item + resultt = Tree()for i in range(10):  t.add(i)print('层序遍历:',t.traverse())print('先序遍历:',t.preorder(t.root))print('中序遍历:',t.inorder(t.root))print('后序遍历:',t.postorder(t.root))

层次遍历: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]先次遍历: [0, 1, 3, 7, 8, 4, 9, 2, 5, 6]中次遍历: [7, 3, 8, 1, 9, 4, 0, 5, 2, 6]后次遍历: [7, 8, 3, 9, 4, 1, 5, 6, 2, 0]