1、广度优先遍历
2、深度优先遍历
先序遍历：把根放在最前面
中序遍历：把根放在中间
后序遍历：把根放在后面
# -*- coding: utf-8 -*-
"""
Created on Mon Feb 25 21:47:53 2019
树的添加
@author: Xavier
"""
class Node(object):
def __init__(self,item):
self.elem=item
self.lchild=None
self.rchild=None
class Tree(object):
#二叉树
def __init__(self):
self.root=None
def add(self,item):
node=Node(item)
if self.root is None:
self.root=node
return
queue=[self.root]
while queue:
cur_node=queue.pop(0)
if cur_node.lchild is None:
cur_node.lchild=node
return
else:
queue.append(cur_node.lchild)
if cur_node.rchild is None:
cur_node.rchild=node
return
else:
queue.append(cur_node.rchild)
def breadth_travel(self):
"""广度遍历"""
if self.root is None:
return
queue=[self.root]
while queue:
cur_node=queue.pop(0)
print(cur_node.elem,end=" ")
if cur_node.lchild is not None:
queue.append(cur_node.lchild)
if cur_node.rchild is not None:
queue.append(cur_node.rchild)
def preorder(self,node):
#先序遍历
#每次使用递归的代码都很简单
if node is None:
return
print(node.elem,end=" ")
self.preorder(node.lchild)
self.preorder(node.rchild)
def inorder(self,node):
#中序遍历
#每次使用递归的代码都很简单
if node is None:
return
self.inorder(node.lchild)
print(node.elem,end=" ")
self.inorder(node.rchild)
def postorder(self,node):
#后序遍历
#每次使用递归的代码都很简单
if node is None:
return
self.postorder(node.lchild)
self.postorder(node.rchild)
print(node.elem,end=" ")
tree=Tree()
tree.add(0)
tree.add(1)
tree.add(2)
tree.add(3)
tree.add(4)
tree.add(5)
tree.add(6)
tree.add(7)
tree.add(8)
tree.add(9)
tree.breadth_travel()
print("")
tree.preorder(tree.root)
print("")
tree.inorder(tree.root)
print("")
tree.postorder(tree.root)
运行结果
runfile('D:/learn_code/code/数据结构与算法python/binary_tree.py', wdir='D:/learn_code/code/数据结构与算法python')
0 1 2 3 4 5 6 7 8 9
0 1 3 7 8 4 9 2 5 6
7 3 8 1 9 4 0 5 2 6
7 8 3 9 4 1 5 6 2 0