数据结构--二叉树（Python实现）

二叉树结构

class Node(object):
    def __init__(self, data, left=None, right=None):
        self.data=data
        self.left=left
        self.right=right

binarytree=Node(1,Node(3,Node(7,Node(0)),Node(6)),Node(2,Node(5),Node(4)))

二叉树遍历

• 层次遍历

def lookup(root):
    print("二叉树层次遍历的结果：",end='')
    stack = [root]
    while stack:
        current=stack.pop(0)
        print(current.data,end='')
        if current.left:
            stack.append(current.left)
        if current.right:
            stack.append(current.right)
    print()
lookup(binarytree)

• 前序遍历

#这是前序遍历二叉树
def preorder(root, order):
    if root==None:
        return
    print(root.data,end='')
    order.append(root.data)
    preorder(root.left, order)
    preorder(root.right, order)
print("二叉树前序遍历的结果：",end='')
pre_order=[]
preorder(binarytree, pre_order) 
print()

• 中序遍历

#这是中序遍历二叉树
def inorder(root, order):
    if root==None:
        return
    inorder(root.left, order)
    print(root.data,end='')
    order.append(root.data)
    inorder(root.right, order)
print("二叉树中序遍历的结果：",end='')
in_order=[]
inorder(binarytree, in_order)
print()

• 后序遍历

#这是后序遍历二叉树
def postorder(root, order):
    if root==None:
        return 
    postorder(root.left, order)
    postorder(root.right, order)
    print(root.data,end='')
    order.append(root.data)
print("二叉树后序遍历的结果：",end='')
post_order=[]
postorder(binarytree, post_order)
print()

根据前序遍历和中序遍历构造二叉树

#根据前序遍历和中序遍历构造二叉树
def construct_tree(pre_order, in_order):
    if len(pre_order)==0:
        return None
    root_data=pre_order[0]
    for i in range(len(in_order)):
        if in_order[i]==root_data:
            break
    left=construct_tree(pre_order[1:i+1],in_order[:i])
    right=construct_tree(pre_order[i+1:],in_order[i+1:])
    return Node(root_data, left, right)
binarytree2=construct_tree(pre_order, in_order)