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package Practice;

import java.util.ArrayList;
import java.util.List;

public class ArrayDemo {

    public static void main(String[] args) {
        TreeNode root = new TreeNode(5);
        TreeNode left = new TreeNode(3);
        TreeNode right = new TreeNode(8);
        TreeNode leftLeft = new TreeNode(2);
        TreeNode leftRight = new TreeNode(4);
        TreeNode rightLeft = new TreeNode(7);
        TreeNode rightRight = new TreeNode(9);

        root.left = left;
        root.right = right;
        left.left = leftLeft;
        left.right = leftRight;
        right.left = rightLeft;
        right.right = rightRight;

        Solution solution = new Solution();
        List<Integer> result = solution.inorderTraversal(root);
        System.out.println(result);
    }
}

class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;

    TreeNode(int val) {
        this.val = val;
    }
}

class Solution {
    public List<Integer> inorderTraversal(TreeNode root) {
        List<Integer> result = new ArrayList<>();
        inorder(root, result);
        return result;
    }

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