二进制搜索树中的节点删除引发错误

时间:2019-02-09 20:24:46

标签: c binary-search-tree coredump

专家,这是我在Binary Search Tree中创建和删除节点的代码。它可以很好地插入,但是在尝试删除节点时(调用deleteNode()函数)会抛出分段错误(核心已转储)。我不明白实际上是什么问题。
请帮忙!预先谢谢你!

#include <stdio.h>
#include <stdlib.h>
int size = 0;
typedef struct mylist{
    int data;
    struct mylist *left;
    struct mylist *right;
}node;
node *root;
void create_root(node *root){
    root = NULL;
}
//Inserting nodes
node* insert(node *root, int val){
    node *ptr, *parentptr, *nodeptr;
    ptr = (node*)malloc(sizeof(node));
    ptr -> data = val;
    ptr -> left = NULL;
    ptr -> right = NULL;
    if(root == NULL)
    root = ptr;
    else{
        parentptr = NULL;
        nodeptr = root;
        while(nodeptr != NULL){
            parentptr=nodeptr;
            if(val < nodeptr -> data)
                nodeptr = nodeptr -> left;
            else
            nodeptr = nodeptr -> right;
        }
        if(val < parentptr -> data)
            parentptr -> left = ptr;
        else
            parentptr -> right = ptr;
    }
    return root;
}

node* minValueNode(node* root) 
{ 
    node* cur = root; 

    while (cur->left != NULL) 
        cur = cur->left; 

    return cur; 
} 

node* deleteNode(node* root, int key) 
{ 
    if (root == NULL){ 
        printf("\nValue not found\n");
    }
    if (key < root-> data)
        root->left = deleteNode(root->left, key); 
    else if (key > root-> data) 
        root->right = deleteNode(root->right, key); 
    else
    { 
        if (root->left == NULL) 
        { 
            node *temp = root->right; 
            free(root);
            return temp; 
        } 
        else if (root->right == NULL) 
        { 
            node *temp = root->left; 
            free(root);
            return temp;  
        } 
        node* temp = minValueNode(root->right);  //Inorder successor
        root->data = temp->data; 
        root->right = deleteNode(root->right, temp->data); 
    }
    return root;
}

void main(){
    int option, val;
    node *ptr;
    int flag = 1;
    create_root(root);
    while(flag != 2){
        printf("\nChoose-\n1-Insert\n2-Delete\n3-Exit\n");
        scanf("%d", &option);
        switch(option){
        case 1:{
            printf("\nEnter the value of new node\n");
            size++;
            scanf("%d", &val);
            root = insert(root, val);
            break;
        }
        case 2:{
            int k;
            printf("Enter the value to delete");
            scanf("%d",&k);
            root=deleteNode(root, k);
            size--;
            break;
        }
        case 3:
            flag=2;
            break;
        default:
            printf("\nWrong entry\n");
        }
    }
}

1 个答案:

答案 0 :(得分:1)

您必须在NULL的第一个if()中返回deleteNode(),或者必须在第二个else之前放置一个if()

node* deleteNode(node* root, int key) 
{ 
    if (root == NULL){ 
        printf("\nValue not found\n");
        return NULL; // <== This was missing.
    }
    ...
}

或替代(也许是故意的?):

node* deleteNode(node* root, int key) 
{ 
    if (root == NULL){ 
        printf("\nValue not found\n");
    }
    else if(key < root->data)        
    ...
}

此刻,即使if(key < root->data)为空,它也会进入下一个root,这会导致段错误。

也:如果可以使用C ++ 11,请使用nullptr