说明

二叉树的前序遍历，中序遍历，后序遍历

代码

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def print_tree(root:TreeNode):
    if root != None:
        print("前序遍历",root.val)
        print_tree(root.left)
        print("中序遍历",root.val)
        print_tree(root.right)
        print("后序遍历",root.val)