/** * File: preorder_traversal_i_compact.java * Created Time: 2023-04-16 * Author: krahets (krahets@163.com) */ package chapter_backtracking; import utils.*; import java.util.*; public class preorder_traversal_i_compact { static List res; /* 前序遍历:例题一 */ static void preOrder(TreeNode root) { if (root == null) { return; } if (root.val == 7) { // 记录解 res.add(root); } preOrder(root.left); preOrder(root.right); } public static void main(String[] args) { TreeNode root = TreeNode.listToTree(Arrays.asList(1, 7, 3, 4, 5, 6, 7)); System.out.println("\n初始化二叉树"); PrintUtil.printTree(root); // 前序遍历 res = new ArrayList<>(); preOrder(root); System.out.println("\n输出所有值为 7 的节点"); List vals = new ArrayList<>(); for (TreeNode node : res) { vals.add(node.val); } System.out.println(vals); } }