Leetcode 94 Given the root node of a binary tree, root, returns its middle-order traversal.

Given the root node of a binary tree, return its middle-order traversal.

/ * *

• Definition for a binary tree node.
• public class TreeNode {

• int val;
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• TreeNode left;
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• TreeNode right;
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• TreeNode() {}
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• TreeNode(int val) { this.val = val; }
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• TreeNode(int val, TreeNode left, TreeNode right) {
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•     this.val = val;
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•     this.left = left;
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•     this.right = right;
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• }
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• }

*/ class Solution { public List inorderTraversal(TreeNode root) { List res = new ArrayList(); inorder(root,res); return res; }

public void inorder(TreeNode root,List<Integer> res){
    if( root == null){
        return;
    }
    inorder(root.left,res);
    res.add(root.val);
    inorder(root.right,res);
}
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}