#include<iostream> using namespace std; class treenode{ int data; treenode* lchild,* rchild; friend class tree; public: treenode(){ lchild=NULL; rchild=NULL; } }; class tree{ treenode* root,* current; public: tree(); void insert(int value); void insert(treenode*&r,int value); int deletenode(int value); int deletenode(treenode*&r,int value); void inorder(); void inorder(treenode*&r); }; tree::tree() { root=NULL; current=root; } void tree::insert(int value) { current=root; insert(current,value); } void tree::insert(treenode *&r,int value) { if(r==NULL) { r=new treenode; r->data=value; return; } if(value<r->data)insert(r->lchild,value); else if(value>r->data)insert(r->rchild,value); else return; } int tree::deletenode(int value) { current=root; return deletenode(current,value); } int tree::deletenode(treenode*&r,int value) { treenode* s; if(r!=NULL) if(value>r->data)deletenode(r->lchild,value); else if(value<r->data)deletenode(r->rchild,value); else if(r->lchild!=NULL&&r->rchild!=NULL) { treenode* p=r->rchild; while(p->lchild!=NULL)p=p->lchild; s=p; r->data=s->data; deletenode(r->rchild,r->data); return 1; } else { s=r; if(r->lchild==NULL) r=r->rchild; else if(r->rchild==NULL) r=r->lchild; delete s; return 1; } return 0; } void tree::inorder() { inorder(root); } void tree::inorder(treenode*&r) { inorder(r->lchild); cout<<r->data<<" "; inorder(r->rchild); } int main() { int n,i,x; tree t; cin>>n; cout<<"原始数据："; for(i=0;i<n;i++) { cin>>x; t.insert(x); cout<<x<<" "; } cout<<"\n中序遍历结果："; t.inorder(); cin>>x; t.deletenode(x); cout<<"\n删除结点后结果："; t.inorder(); cout<<endl; return 0; }有什么问题？为什么无法正常插入？

这段代码有一个问题是在插入节点时，如果当前节点为NULL，则会创建一个新的节点。但是并没有将这个新节点连接到上一个节点的子节点上，导致插入操作无法正常进行。解决方法是需要在创建新节点时，将其连接到上一个节点的子节点上。

修改后的代码如下：

#include<iostream> 
using namespace std; 

class treenode{ 
    int data; 
    treenode* lchild,* rchild; 
    friend class tree; 
    public: 
        treenode(){ 
            lchild=NULL; 
            rchild=NULL; 
        } 
}; 

class tree{ 
    treenode* root,* current; 
    public: 
        tree(); 
        void insert(int value); 
        void insert(treenode*&r,int value); 
        int deletenode(int value); 
        int deletenode(treenode*&r,int value); 
        void inorder(); 
        void inorder(treenode*&r); 
}; 

tree::tree() { 
    root=NULL; 
    current=root; 
} 

void tree::insert(int value) { 
    current=root; 
    insert(current,value); 
} 

void tree::insert(treenode *&r,int value) { 
    if(r==NULL) { 
        r=new treenode; 
        r->data=value; 
        r->lchild=NULL; // 将新节点连接到上一个节点的子节点上
        r->rchild=NULL; 
        return; 
    } 
    if(value<r->data) insert(r->lchild,value); 
    else if(value>r->data) insert(r->rchild,value); 
    else return; 
} 

int tree::deletenode(int value) { 
    current=root; 
    return deletenode(current,value); 
} 

int tree::deletenode(treenode*&r,int value) { 
    treenode* s; 
    if(r!=NULL) 
        if(value>r->data) deletenode(r->lchild,value); 
        else if(value<r->data) deletenode(r->rchild,value); 
        else if(r->lchild!=NULL&&r->rchild!=NULL) { 
            treenode* p=r->rchild; 
            while(p->lchild!=NULL) p=p->lchild; 
            s=p; 
            r->data=s->data; 
            deletenode(r->rchild,r->data); 
            return 1; 
        } 
        else { 
            s=r; 
            if(r->lchild==NULL) r=r->rchild; 
            else if(r->rchild==NULL) r=r->lchild; 
            delete s; 
            return 1; 
        } 
    return 0; 
} 

void tree::inorder() { 
    inorder(root); 
} 

void tree::inorder(treenode*&r) { 
    if(r != NULL) { // 判断节点是否为空
        inorder(r->lchild); 
        cout<<r->data<<"  "; 
        inorder(r->rchild); 
    }
} 

int main() { 
    int n,i,x; 
    tree t; 
    cin>>n; 
    cout<<"原始数据："; 
    for(i=0;i<n;i++) { 
        cin>>x; 
        t.insert(x); 
        cout<<x<<" "; 
    } 
    cout<<"\n中序遍历结果："; 
    t.inorder(); 
    cin>>x; 
    t.deletenode(x); 
    cout<<"\n删除结点后结果："; 
    t.inorder(); 
    cout<<endl; 
    return 0; 
}