hello-algo/codes/csharp/chapter_backtracking/preorder_traversal_i_compact.cs

/**
 * File: preorder_traversal_i_compact.cs
 * Created Time: 2023-04-17
 * Author: hpstory (hpstory1024@163.com)
 */

namespace hello_algo.chapter_backtracking;

public class preorder_traversal_i_compact {
    static List<TreeNode> 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);
    }

    [Test]
    public void Test() {
        TreeNode root = TreeNode.ListToTree(new List<int?> { 1, 7, 3, 4, 5, 6, 7 });
        Console.WriteLine("\n初始化二叉树");
        PrintUtil.PrintTree(root);

        // 前序遍历
        res = new List<TreeNode>();
        preOrder(root);

        Console.WriteLine("\n输出所有值为 7 的节点");
        PrintUtil.PrintList(res.Select(p => p.val).ToList());
    }
}