class Node:
def __init__(self, data, left=None, right=None):
self.data, self.left, self.right = data, left, right
class BinTree:
def __init__(self, root=None):
self.root = root
self.callback = []
@classmethod
def build_from(cls, node_list):
"""通过节点信息构造二叉树
第一次遍历我们构造 node 节点
第二次遍历我们给 root 和 孩子赋值
:param node_list: {'data': 'A', 'left': None, 'right': None, 'is_root': False}
"""
node_dict = {}
root = None
for node_data in node_list:
node_dict[node_data['data']] = Node(node_data['data']) # 所有节点写入节点字典中
for node_data in node_list:
data = node_data['data']
node = node_dict[data] # node_dict = {'A':Node('A')}
if node_data['is_root']:
root = node
node.left = node_dict.get(node_data['left']) # Node('A').left = Node('B') else None
node.right = node_dict.get(node_data['right'])
return cls(root)
def preorder_traverse(self, subtree):
'''
先(根)序遍历
:param subtree:
:return:
'''
if subtree is not None: # 该节点没有子节点就停止
print(subtree.data)
self.preorder_traverse(subtree.left)
self.preorder_traverse(subtree.right)
def midorder_traverse(self, subtree):
'''
中(根)序遍历
:param subtree:
:return:
'''
if subtree is not None:
self.midorder_traverse(subtree.left)
print(subtree.data)
self.midorder_traverse(subtree.right)
def lastorder_traverse(self, subtree):
'''
后(根)序遍历
:param subtree:
:return:
'''
if subtree is not None:
self.lastorder_traverse(subtree.left)
self.lastorder_traverse(subtree.right)
self.callback.append(subtree.data)
def reverse(self, subtree):
if subtree is not None:
subtree.left, subtree.right = subtree.right, subtree.left
self.reverse(subtree.left)
self.reverse(subtree.right)
node_list = [
{'data': 'A', 'left': 'B', 'right': 'C', 'is_root': True},
{'data': 'B', 'left': 'D', 'right': 'E', 'is_root': False},
{'data': 'D', 'left': None, 'right': None, 'is_root': False},
{'data': 'E', 'left': 'H', 'right': None, 'is_root': False},
{'data': 'H', 'left': None, 'right': None, 'is_root': False},
{'data': 'C', 'left': 'F', 'right': 'G', 'is_root': False},
{'data': 'F', 'left': None, 'right': None, 'is_root': False},
{'data': 'G', 'left': 'I', 'right': 'J', 'is_root': False},
{'data': 'I', 'left': None, 'right': None, 'is_root': False},
{'data': 'J', 'left': None, 'right': None, 'is_root': False},
]
def tree(node_list):
nodes = {}
datas = []
root = None
for nodedata in node_list:
data = nodedata['data']
left = nodedata['left']
right = nodedata['right']
nodes[data] = Node(data, left, right)
datas.append(data)
# 所有节点均有了，nodes= {'A':Node('A'),'B':Node('B')}
# Node('A'):{'data':'A',left:'B',right:'C'}
for nodedata in node_list:
data = nodedata['data'] # 'A','B','C'
node = nodes[data]
if nodedata['is_root']:
root = node
try:
node.left = nodes[node.left]
except KeyError:
node.left = None
node.right = nodes.get(nodedata['right'])
return root
if __name__ == '__main__':
btree = BinTree.build_from(node_list)
# btree.preorder_traverse(btree.root) # 输出 A, B, D, E, H, C, F, G, I, J
# btree.midorder_traverse(btree.root)
btree.lastorder_traverse(btree.root)
print(btree.callback)
btree.reverse(btree.root)
print(btree.root)
