如何删除树中的节点？

Posted 2023-02-22

【中文标题】如何删除树中的节点？

【英文标题】：How to delete a node in a tree?

【发布时间】：2014-02-26 13:16:28

【问题描述】：

我正在尝试使用指针在 C++ 中实现一个简单的二叉树。

我已经成功实现了插入和遍历，但是我在尝试删除节点时遇到了一些问题：

我的主要功能是：

main()
node* root=createNode(1);
root->left=createNode(2);
root->right=createNode(3);
root->left->left=createNode(4);
root->left->right=createNode(5);
root->right->left=createNode(6);
root->right->right=createNode(7);
inorder(root);
//till here it works fine

delete root->left->left;     //problem starts here
cout<<"\n";
inorder(root);               //exception is thrown here...
return 0;

`

中序函数是非常基本的递归函数：

void inorder(node* root)
if(root!=NULL)
    inorder(root->left);
    cout<<root->data<<" ";
    inorder(root->right);

谁能告诉我删除行有什么问题？

【问题讨论】：

抛出什么异常？你确定这是个例外吗？

createNode 是否将left 和right 指针设置为null？

@JosephMansfield，我敢打赌是 sigsegv 导致应用程序崩溃。

【参考方案1】：

在delete 之后，尝试访问已删除的指针会导致此问题。你可能想添加

root->left->left = 0

在删除行之后。

【参考方案2】：

您必须将 root->left->left 指针设置为 NULL，即它没有任何意义

在你的代码中

main()

   node* root=createNode(1);
   root->left=createNode(2);
   root->right=createNode(3);
   root->left->left=createNode(4);
   root->left->right=createNode(5);
   root->right->left=createNode(6);
   root->right->right=createNode(7);
   inorder(root);
   //Now, Complete program will work

   delete root->left->left =  0;     //problem solved
   cout<<"\n";
   inorder(root);               // Do you still face any problem ?
   return 0;

【参考方案3】：

删除节点后，需要将父节点的左指针重置为零。 不这样做可能会导致不可预知的结果，具体取决于内存管理的实现方式。一些系统对释放内存的引用表示例外

【参考方案4】：

Your trying to delete node which has not null nodes in both right and left side, so you to delete node like this ..

/* deletes a node from the binary search tree */
void delete ( struct btreenode **root, int num )

    int found ;
    struct btreenode *parent, *x, *xsucc ;

    /* if tree is empty */
if ( *root == NULL )
    
        printf ( "\nTree is empty" ) ;
        return ;
    

    parent = x = NULL ;

    /* call to search function to find the node to be deleted */

    search ( root, num, &parent, &x, &found ) ;

    /* if the node to deleted is not found */
if ( found == FALSE )
    
        printf ( "\nData to be deleted, not found" ) ;
        return ;
    

    /* if the node to be deleted has two children */
if ( x -> leftchild != NULL && x -> rightchild != NULL )
    
        parent = x ;
        xsucc = x -> rightchild ;

        while ( xsucc -> leftchild != NULL )
        
            parent = xsucc ;
            xsucc = xsucc -> leftchild ;
        

        x -> data = xsucc -> data ;
        x = xsucc ;
    

    /* if the node to be deleted has no child */
if ( x -> leftchild == NULL && x -> rightchild == NULL )
    
        if ( parent -> rightchild == x )
            parent -> rightchild = NULL ;
        else
            parent -> leftchild = NULL ;

        free ( x ) ;
        return ;
    

    /* if the node to be deleted has only rightchild */
if ( x -> leftchild == NULL && x -> rightchild != NULL )
    
        if ( parent -> leftchild == x )
            parent -> leftchild = x -> rightchild ;
        else
            parent -> rightchild = x -> rightchild ;

        free ( x ) ;
        return ;
    

    /* if the node to be deleted has only left child */
if ( x -> leftchild != NULL && x -> rightchild == NULL )
    
        if ( parent -> leftchild == x )
            parent -> leftchild = x -> leftchild ;
        else
            parent -> rightchild = x -> leftchild ;

        free ( x ) ;
        return ;