c - 为什么在删除节点时出现分段错误？

Question

    node * del(node * start,int loc)
{
    int l=len(start);
    if(loc<1 || loc>l)
    {
        printf("Deletion not possible. \n");
    }
    else
    {
        if(loc==1)
        {
            node *p;
            p=start;
            start=start->next;
            free(p);
        }
        else
        {
            node *p,*q;
            p=start;
            for(int i=1;i<=loc-1;i++)//check this one.
            {
                q=p;
                p=p->next;
            }
            q->next=p->next;
            free(p);
        }       
        printf("Deletion completed!\n");
    }
    return start;
}

这是函数，我从 main() 调用它：

case 5:
            printf("Enter the node you want to delete. \n");
            scanf("%d",temp);
            start=del(start,temp);
            break;

在删除任何节点时，我遇到了分段错误！我被困在这个问题上。任何人都可以帮忙吗？

这是完整的程序：-

#include<stdio.h>
#include<stdbool.h>
#include<stdlib.h>

struct Node
{
    int data;
    struct Node * next;
};

typedef struct Node node;

int len(node * start)
{
    if(start==NULL)
        return 0;
    int c=1;
    while(start!=NULL)
    {
        start=start->next;
        c++;
    }
    return c;
}
node * insert(node* start,int loc,int d)
{
    int l=len(start);
    node * p=start;
    node * temp=(node*)malloc(sizeof(node));
    if(loc<1 || loc>l+1)
    {
        printf("Insertion not posible.!\n");
        return start;
    }       
    if(l==0 || loc==1)
    {
        temp->next=start;
        start=temp;
        temp->data=d;
        printf("Insertion completed.\n");
    }
    else
    {
        for(int i=1;i<=loc-2;i++)
        p=p->next;
        temp->next=p->next;
        p->next=temp;
        temp->data=d;
        printf("Insertion completed. \n");
    }   
    return start;
}
void show(node *start)
{
    int l=len(start);
    if(l==0)
    {
        printf("Nothing to print. \n");
    }
    else
    {
        for(int i=1;i<l-1;i++)
        {
            printf(" %d -> ",start->data);
            start=start->next;
        }
        printf(" %d \n",start->data);
    }   
}
node * destroy(node * start)
{
    node * p=start;
    while(start!=NULL)
    {
        start=start->next;
        free(p);
        p=start;
    }
    printf("Destroy of linked list completed! .\n");
    return NULL;
}
node * del(node * start,int loc)
{
    int l=len(start);
    if(loc<1 || loc>l)
    {
        printf("Deletion not possible. \n");
    }
    else
    {
        if(loc==1)
        {
            node *p;
            p=start;
            start=start->next;
            free(p);
        }
        else
        {
            node *p,*q;
            p=start;
            for(int i=1;i<=loc-1;i++)//check this one.
            {
                q=p;
                p=p->next;
            }
            q->next=p->next;
            free(p);
        }       
        printf("Deletion completed!\n");
    }
    return start;
}
int main()
{
    node * start=NULL;
    int ch,temp,d;
    ch=temp=d=0;
    while(ch != -1)
    {
        switch(ch)
        {
            case 0:
            printf("Enter 0 to show menu.\n");
            printf("Enter 1 to create linked list.\n");
            printf("Enter 2 to destroy linked list.\n");
            printf("Enter 3 to get the length of likned list.\n");
            printf("Enter 4 to insert element in the linked list.\n");
            printf("Enter 5 to delete element from the linked list.\n");
            printf("Enter 6 to view the linked list.\n");
            printf("Enter 7 to reverse a linked list.\n");
            break;

            case 1:
            printf("Enter the size of link list to begin with.\n");
            scanf("%d",&temp);
            for(int i=1;i<=temp;i++)
            {
                printf("Enter the data to bes inserted to node %d .\n",i);
                scanf("%d",&d);
                start=insert(start,i,d); 
            }
            break;

            case 2:
            start=destroy(start);
            break;

            case 3:
            printf("Size of linked list is: %d \n",len(start));
            break;

            case 4:
            printf("Enter the location where you want to insert the data.\n");
            scanf("%d",&temp);
            printf("Enter the data to be intered.\n");
            scanf("%d",&d);
            start=insert(start,temp,d);
            break;

            case 5:
            printf("Enter the node you want to delete. \n");
            scanf("%d",temp);
            start=del(start,temp);
            break;

            case 6:
            show(start);
            break;

            default:
            ch=0;
            break;
        }
        printf("\nEnter your choice? \n");
        scanf("%d",&ch);
    }
    destroy(start);


}

标签： cpointersdata-structureslinked-listsegmentation-fault

Answer 1

改变：

    case 5:
    printf("Enter the node you want to delete. \n");
    scanf("%d",temp);
    start=del(start,temp);
    break;

线scanf("%d",temp);到scanf("%d",&temp);