package org.example.leetcodeBook.deepSearch;
import java.util.ArrayList;
import java.util.List;
public class PreorderTraversalSolution {
public List<Integer> preorderTraversal(TreeNode root){
ArrayList<Integer> res = new ArrayList<>();
preorder(root,res);
return res;
}
public void preorder(TreeNode root,List<Integer> res){
if(root==null)return;
res.add(root.val);
preorder(root.left,res);
preorder(root.right,res);
}
}