请输出c++代码，实现树的节点增加 删减 查找

以下是一个简单的树结构的 C++ 实现，包括节点的增加、删除和查找功能：

#include<iostream>
#include<vector>

using namespace std;

struct TreeNode{
    int val;
    vector<TreeNode*> children;
    TreeNode(int x): val(x){}
};

class Tree{
public:
    Tree(){
        root = NULL;
    }
    
    // 添加节点
    void addNode(int parent_val, int val){
        TreeNode* new_node = new TreeNode(val);
        if(!root){
            root = new_node;
            return;
        }
        TreeNode* parent = findNode(root, parent_val);
        parent->children.push_back(new_node);
    }
    
    // 删除节点
    void deleteNode(int val){
        TreeNode* node = findNode(root, val);
        if(!node){
            cout << "Node not found!" << endl;
            return;
        }
        if(node == root){
            delete root;
            root = NULL;
            return;
        }
        TreeNode* parent = findParent(root, val);
        for(int i=0; i<parent->children.size(); i++){
            if(parent->children[i]->val == val){
                parent->children.erase(parent->children.begin() + i);
                break;
            }
        }
        delete node;
    }
    
    // 查找节点
    TreeNode* findNode(TreeNode* node, int val){
        if(!node) return NULL;
        if(node->val == val) return node;
        for(int i=0; i<node->children.size(); i++){
            TreeNode* found = findNode(node->children[i], val);
            if(found) return found;
        }
        return NULL;
    }
    
private:
    TreeNode* root;
    
    // 查找节点的父节点
    TreeNode* findParent(TreeNode* node, int val){
        if(!node || node->val == val) return NULL;
        for(int i=0; i<node->children.size(); i++){
            if(node->children[i]->val == val) return node;
            TreeNode* parent = findParent(node->children[i], val);
            if(parent) return parent;
        }
        return NULL;
    }
};

int main(){
    Tree t;
    t.addNode(0, 1);
    t.addNode(1, 2);
    t.addNode(1, 3);
    t.addNode(2, 4);
    t.addNode(2, 5);
    t.addNode(3, 6);
    
    TreeNode* found = t.findNode(t.root, 2);
    if(found) cout << found->val << endl;
    
    t.deleteNode(2);
    found = t.findNode(t.root, 2);
    if(found) cout << found->val << endl;
    else cout << "Node not found!" << endl;
    
    return 0;
}

这个实现中，树节点的结构体包括节点值和一个指向其所有子节点的向量。树类中实现了添加节点、删除节点和查找节点的方法。其中，查找节点的方法使用了递归实现。