C - Linked List - Delete Node

Question

This is suppose to delete all the nodes containing the data "last" which is the same as the string "name". It is not giving me an error, but it is not working properly.It deletes more than what it needs to delete.

struct node* mydelete(struct node *head) {
    char name[21];
    struct node *temp;

    printf("---Please enter last name:");
    scanf("%s", &name);
    while (head->next != NULL) {
        if (strcmp(head->last,name) == 0) {
            temp = head;
            head = head->next;
            free(temp);
            n--;
        } else if (strcmp(head->next->last,name)==0) {
            temp = head->next;
            head->next = head->next->next;
            free(temp);
            n--;
        } else
            head = head->next;
    }

    return head;
}

Would you also post the test case and execution result?

poiu2000
– poiu2000

2013-12-01 07:03:37 +00:00
Commented Dec 1, 2013 at 7:03 — poiu2000
– poiu2000, Commented Dec 1, 2013 at 7:03
I'm trying to delete all nodes that contain the "name"

user3053814
– user3053814

2013-12-01 19:57:41 +00:00
Commented Dec 1, 2013 at 19:57 — user3053814
– user3053814, Commented Dec 1, 2013 at 19:57

SliceSort · Accepted Answer · 2013-12-02 02:06:22Z

1

return head

is wrong. When you move the head forward(to "next"), anything it passed will lost -- you maybe not free some of them, but you can't get them anymore. You should use temp pointer to hold first node in the list(after deletion), and return it at last.

And, don't forget if head == NULL.

.

Modified from your code:

struct node *first = NULL;
while(head != NULL)
{
    if(strcmp(head->last,name)==0)
    {   //delete head
        temp = head;
        head = head->next;
        free(temp);
        n--;
    }
    else
    {   //delete head->next

        if (first == NULL)
            first = head;

        if (head->next == NULL)
            break;

        if(strcmp(head->next->last,name)==0)
        {
            temp = head->next;
            head->next = head->next->next;
            free(temp);
            n--;
        }
        else
            head = head->next;
    }
}

return first;

edited Dec 2, 2013 at 2:06

answered Dec 1, 2013 at 6:51

SliceSort

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1 Comment

SliceSort Over a year ago

@user3053814 I had a error: "bread" should be "break". Code has been corrected.

Sztrovacsek · Accepted Answer · 2013-12-01 06:27:31Z

0

Firstly, your code crashes if you call with head == NULL, which can very well happen (if your list is empty). So, check for that. Secondly, there is no reason why you need to check the string name against two different nodes of the list. Just skip the else if branch. Thirdly, if you want to delete just one node which matches your test, then break from the while cycle after you deleted it.

answered Dec 1, 2013 at 6:27

Sztrovacsek

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Comments

EmptyData · Accepted Answer · 2013-12-01 06:34:15Z

0

You do not need the else if condition in your code of delete. If more then one element is deleting it means that your list contain more then one element with same name. First check your list contents .

answered Dec 1, 2013 at 6:34

EmptyData

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