package LeetCode;

import java.util.ArrayList;

public class LC_98 {
    public static void main(String[] args) {

    }

    public boolean isValidBST(TreeNode root) {
        if (root == null) return false;
        if (root.left == null && root.right == null) return true;
        ArrayList<Integer> list = new ArrayList<>();
        traversal(root, list);
        for (int i = 0; i < list.size()-1; i++) {
            if(list.get(i)>=list.get(i+1)) return false;
        }
        return true;
    }

    public static void traversal(TreeNode root, ArrayList<Integer> list) {
        if (root == null) return;
        traversal(root.left, list);
        list.add(root.val);
        traversal(root.right, list);
    }
}