Binary Tree Inorder Traversal

 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]
class Solution {
    List<Integer> list = new ArrayList<Integer>();
    public List<Integer> inorderTraversal(TreeNode root) {        
        if(root==null) return new ArrayList<Integer>();        
        inorderTraversal(root.left);
        list.add(root.val);        
        inorderTraversal(root.right);
        
        return list;
    }
}




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