二叉树的前序遍历

40 阅读1分钟
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);  
    }  
}