#coding:utf-8 class node(): def __init__(self,k=None,l=None,r=None): self.key=k; self.left=l; self.right=r; def create(root): a=input('enter a key:'); if a is '#': root=None; else: root=node(k=a); root.left=create(root.left); root.right=create(root.right); return root; def preorder(root): #前序遍历 if root is None: return ; else : print(root.key,end=''); preorder(root.left); preorder(root.right); def inorder(root): #中序遍历 if root is None: return ; else: inorder(root.left); print(root.key,end=''); inorder(root.right); def postorder(root): # 后序遍历 if root is None: return ; else : postorder(root.left); postorder(root.right); print(root.key,end=''); root=None; # 测试代码 root=create(root); preorder(root); print(' ') inorder(root); print(' ') postorder(root);