class Node:
def __init__(self,value):
self.value = value
self.right = None
self.left = None
class Tree:
def __init__(self,root):
self.root = Node(root)
def print_tree(self):
return self.preorder_print(self.root,"")
def preorder_print(self,start,traversal):
if start:
print('step 1')
traversal = self.preorder_print(start.left, traversal)
print('step 2')
traversal +=(str(start.value)+"-")
print('step 3')
traversal = self.preorder_print(start.right, traversal)
return traversal
"""
F
B G
A D I
C E H
In- order print: A->B->C->D->E->F->G->H->I
"""
tree = Tree("F")
tree.root.left = Node("B")
tree.root.right = Node("G")
tree.root.right.right = Node("I")
tree.root.right.right.left = Node("H")
tree.root.left.left = Node("A")
tree.root.left.right = Node("D")
tree.root.left.right.left = Node("C")
tree.root.left.right.right = Node("E")
print(tree.print_tree())
Node A
时,递归确实有所帮助。if start:
语句中的函数突破了递归(基本情况)。顺便说一下,您发布的代码将输出以下内容:A-B-C-D-E-F-G-H-I-