题解 | #实现二叉树先序，中序和后序遍历#

result_pre = []
result_mid = []
result_post = []
class Solution:
    def threeOrders(self , root: TreeNode) -> List[List[int]]:
        # write code here
        self.preOrder(root)
        self.midOrder(root)
        self.postOrder(root)
        result = [result_pre,result_mid,result_post]
        return result
        
    def preOrder(self, root: TreeNode):
        if not root:
            return
        result_pre.append(root.val)
        self.preOrder(root.left)
        self.preOrder(root.right)
    
    def midOrder(self, root: TreeNode):
        if not root:
            return
        self.midOrder(root.left)
        result_mid.append(root.val)
        self.midOrder(root.right)
        
    def postOrder(self, root: TreeNode):
        if not root:
            return
        self.postOrder(root.left)
        self.postOrder(root.right)
        result_post.append(root.val)