C#实现前缀树时节点属性修改不生效，无需指针如何解决？

你遇到的问题核心是**Node被定义为struct（值类型）**而非class（引用类型）。在C#中，值类型变量赋值时会创建完整副本，所以你执行tmp.end = true时，只是修改了栈上的临时副本，字典里存储的实际Node实例完全不受影响——这和C++里指针/引用操作同一块内存的逻辑本质不同。

把Node从struct改成class，所有操作就会基于引用执行，修改tmp的属性会直接作用于字典中存储的实际节点。

public class Node
{
    public char val;
    public bool end;
    public Dictionary<char, Node> children;
    public Node(char val)
    {
        this.val = val;
        end = false;
        children = new Dictionary<char, Node>();
    }
}

public class Solution
{
    public string ReplaceWords(IList<string> dictionary, string sentence)
    {
        Node head = new Node('a');
        foreach (var word in dictionary)
        {
            Node tmp = head;
            for (int i = 0; i < word.Length; i++)
            {
                char charact = word[i];
                if (!tmp.children.ContainsKey(charact))
                {
                    Node newNode = new Node(charact);
                    tmp.children.Add(charact, newNode);
                }
                tmp = tmp.children[charact];
            }
            // 现在修改的是引用指向的实际节点属性，会同步到前缀树中
            tmp.end = true;
        }

        StringBuilder res = new StringBuilder();
        string[] words = sentence.Split(' ');
        for (int i = 0; i < words.Length; i++)
        {
            string word = words[i];
            Node travel = head;
            StringBuilder tmpStr = new StringBuilder();
            bool foundRoot = false;
            foreach (var charact in word)
            {
                if (travel.children.ContainsKey(charact))
                {
                    tmpStr.Append(charact);
                    travel = travel.children[charact];
                    if (travel.end)
                    {
                        foundRoot = true;
                        break;
                    }
                }
                else
                {
                    break;
                }
            }
            res.Append(foundRoot ? tmpStr.ToString() : word);
            if (i != words.Length - 1)
            {
                res.Append(' ');
            }
        }
        return res.ToString();
    }
}

• 用StringBuilder替代字符串拼接，避免频繁创建字符串对象，提升大数据量场景下的性能。
• 调整前缀查找逻辑，用foundRoot标记更清晰，避免提前覆盖临时字符串。

内容的提问来源于stack exchange，提问作者Masterdemon123