python 实现二叉树
class BinTreeNode(object): def __init__(self, data, left = None, right = None): self.left = left self.right = right self.data = data 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}, ] # 其实BinTree的作用就是把每一个结点链接起来 class BinTree(object): def __init__(self, root = None): self.root = root # classmethod 修饰符对应的函数不需要实例化,不需要 self 参数, # 但第一个参数需要是表示自身类的 cls 参数,可以来调用类的属性,类的方法,实例化对象等。 @classmethod def build_from(cls, node_list): """ 通过结点信息构造二叉树,。 第一次遍历构造node结点,第二次遍历,我们给root和孩子赋值。 最后我们用root初始化这个类,并且返回一个对象 """ node_dict = {} # 字典 for node_data in node_list: data = node_data['data'] node_dict[data] = BinTreeNode(data) # 构造了结点 for node_data in node_list: data = node_data['data'] node = node_dict[data] if node_data['is_root']: root = node # 之前已经把所有的结点都加入到node_dict里面了。 node.left = node_dict.get(node_data['left']) node.right = node_dict.get(node_data['right']) return cls(root) def preorder_trav(self, subtree): # 先序遍历 if subtree is not None: print(subtree.data) # 递归函数里面先处理根 self.preorder_trav(subtree.left) self.preorder_trav(subtree.right) def midorder_trav(self, subtree): if subtree is not None: self.preorder_trav(subtree.left) print(subtree.data) # 递归函数里面先处理根 self.preorder_trav(subtree.right) def afterorder_trav(self, subtree): if subtree is not None: self.preorder_trav(subtree.left) self.preorder_trav(subtree.right) print(subtree.data) # 递归函数里面先处理根 # 反转二叉树 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) btree = BinTree.build_from(node_list) print("先序遍历") btree.preorder_trav(btree.root) print("中序遍历") btree.midorder_trav(btree.root) print("后序遍历") btree.afterorder_trav(btree.root) btree.reverse(btree.root) print("反转后后序遍历") btree.afterorder_trav(btree.root)