题解 | #二叉树的前序遍历#

递归求解

class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param root TreeNode类 
# @return int整型一维数组
#
class Solution:
    def preorderTraversal(self , root: TreeNode):
        # write code here
        if root != None:
            try:
                list_val.append(root.val)
            except:
                list_val = [root.val]
            left_list = self.preorderTraversal(root.left)
            if left_list != None:
                list_val.extend(left_list)
            right_list = self.preorderTraversal(root.right)
            if right_list != None:
                list_val.extend(right_list)
            return list_val

root = TreeNode(1)
root.right = TreeNode(2)
root.right.left = TreeNode(3)
print(Solution().preorderTraversal(root))