Binary Tree Inorder Traversal

94. Binary Tree Inorder Traversal

Difficulty: Easy

Related Topics: Stack, Tree, DFS, Binary Tree

Given the root of a binary tree, return the inorder traversal of its nodes’ values.

Example 1:

Input: root = [1,null,2,3] Output: [1,3,2]

Example 2:

Input: root = [] Output: []

Example 3:

Input: root = [1] Output: [1]

Code:

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def inorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
        def helper(root, values):
            if root:
                helper(root.left, values)
                values.append(root.val)
                helper(root.right,values)
        values = []
        helper(root,values)
        return values