Python定义二叉树及4种遍历方法实例详解

# init a tree
def InitBinaryTree(dataSource, length):
  root = BTNode(dataSource[0])
  for x in xrange(1,length):
    node = BTNode(dataSource[x])
    InsertElementBinaryTree(root, node)
  return root
  print 'Done...'

# pre-order
def PreorderTraversalBinaryTree(root):
  if root:
    print '%d | ' % root.data,
    PreorderTraversalBinaryTree(root.leftChild)
    PreorderTraversalBinaryTree(root.rightChild)

# in-order
def InorderTraversalBinaryTree(root):
  if root:
    InorderTraversalBinaryTree(root.leftChild)
    print '%d | ' % root.data,
    InorderTraversalBinaryTree(root.rightChild)

# post-order
def PostorderTraversalBinaryTree(root):
  if root:
    PostorderTraversalBinaryTree(root.leftChild)
    PostorderTraversalBinaryTree(root.rightChild)
    print '%d | ' % root.data,

# layer-order
def TraversalByLayer(root, length):
  stack = []
  stack.append(root)
  for x in xrange(length):
    node = stack[x]
    print '%d | ' % node.data,
    if node.leftChild:
      stack.append(node.leftChild)
    if node.rightChild:
      stack.append(node.rightChild)

# -*- coding:utf-8 -*-
#################
### implement Binary Tree using python
### Hongwing
### 2016-9-4
#################
import math
class BTNode(object):
  """docstring for BTNode"""
  def __init__(self, data):
    self.data = data
    self.leftChild = None
    self.rightChild = None
# insert element
def InsertElementBinaryTree(root, node):
  if root:
    if node.data < root.data:
      if root.leftChild:
        InsertElementBinaryTree(root.leftChild, node)
      else:
        root.leftChild = node
    else:
      if root.rightChild:
        InsertElementBinaryTree(root.rightChild, node)
      else:
        root.rightChild = node
  else:
    return 0
# init a tree
def InitBinaryTree(dataSource, length):
  root = BTNode(dataSource[0])
  for x in xrange(1,length):
    node = BTNode(dataSource[x])
    InsertElementBinaryTree(root, node)
  return root
  print 'Done...'
# pre-order
def PreorderTraversalBinaryTree(root):
  if root:
    print '%d | ' % root.data,
    PreorderTraversalBinaryTree(root.leftChild)
    PreorderTraversalBinaryTree(root.rightChild)
# in-order
def InorderTraversalBinaryTree(root):
  if root:
    InorderTraversalBinaryTree(root.leftChild)
    print '%d | ' % root.data,
    InorderTraversalBinaryTree(root.rightChild)
# post-order
def PostorderTraversalBinaryTree(root):
  if root:
    PostorderTraversalBinaryTree(root.leftChild)
    PostorderTraversalBinaryTree(root.rightChild)
    print '%d | ' % root.data,
# layer-order
def TraversalByLayer(root, length):
  stack = []
  stack.append(root)
  for x in xrange(length):
    node = stack[x]
    print '%d | ' % node.data,
    if node.leftChild:
      stack.append(node.leftChild)
    if node.rightChild:
      stack.append(node.rightChild)
if __name__ == '__main__':
  dataSource = [3, 4, 2, 6, 7, 1, 8, 5]
  length = len(dataSource)
  BTree = InitBinaryTree(dataSource, length)
  print '****NLR:'
  PreorderTraversalBinaryTree(BTree)
  print '\n****LNR'
  InorderTraversalBinaryTree(BTree)
  print '\n****LRN'
  PostorderTraversalBinaryTree(BTree)
  print '\n****LayerTraversal'
  TraversalByLayer(BTree, length)