Python编程实现双链表，栈，队列及二叉树的方法示例
本文实例讲述了Python编程实现双链表，栈，队列及二叉树的方法。分享给大家供大家参考，具体如下：
1.双链表
class Node(object):
def __init__(self, value=None):
self._prev = None
self.data = value
self._next = None
def __str__(self):
return "Node(%s)"%self.data
class 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
2. 栈
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
3.队列
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
4. 二叉树（定义与遍历）
class Node:
def __init__(self,item):
self.item = item
self.child1 = None
self.child2 = None
class 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 + result
t = 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))
输出结果：
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]
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