Thread: delete an element from a linked list

Hi,

I would like to delete an element from a singled linked list, I have the written the function, but I have some troubles calling it.

The program accepts any words and stores them in the linked list. But How can I delete one of the word entered by the user ?

here's my code:

Code:

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

struct list  {
  char word [ 50 ]; // words entered by the user
  struct list * next;  //our structure
  };

void Printlist (struct list * ); //prototype to display the linked list

/*  Deleting an element */

void mdelete( struct list *p,
              struct list *i,
              struct list **start,
              struct list **last)
{
    if(p) p->next = i->next;
    else *start = i->next;
    if(i==*last && p) *last = p;
}

int main ( void )
{ int choice;
  struct list *start, *p;
  start = malloc ( sizeof (struct list));
  start->next = NULL;

do {
    printf("\n\n\t 1.  Add a word");
    printf("\n\t 2.  Delete a word");
    printf("\n\t 3.  Search for and display");
    printf("\n\t 4.  Display data in queue order");
    printf("\n\t 5.  Quit");
    printf("\n\n\t Enter your choice : ");
    scanf("%i", & choice);

    if ( choice == 1 ) {
      for(p = start; p->next != NULL; p = p->next){}   // puts the word after the last one
      p->next = malloc (sizeof(struct list));
      p->next->next = NULL;
      printf("\n\tEnter the word to add : ");
      scanf("%s", p->word);
     }

    if ( choice == 2 ) {
        printf("\n\tEnter the word to delete : ");
        scanf("%s", ???); // here's my problem, I need to know what should be inside scanf
        mdelete( ??? );  // What the parameters should be here?
        Printlist ( start );
        }

    if ( choice == 4 ) {
        Printlist ( start );
        }

    } while ( choice != 5 );

return 0;

Thanks for your help

I am too sleepy to understand your code now.Specially a long linkedlist one.But I can write:

Code:

typedef struct linkedlist {
char word[100];
struct linkedlist *next; } newnode;

int main() {
newnode *startptr=NULL;
fgets(s,50,stdin);
delete(&startptr,s);
return 0;
}

void delete(newnode **sptr,char *d) {
newnode *previous,*current,*temp;


previous=NULL;
current=*sptr;
while((strcmp(current->word,d))!=0 && current!=NULL) {
previous=current;
current=current->next; }

if(previous==NULL) {
printf("There is not d here or linkedlist is empty"); }
else {
if(current==NULL) {
printf("there is no d definitely"); }
else {
temp=current;
previous->next=current->next;
free(temp); }
}

My friends. It is probably full of bugs. Maybe I used freakishly long ways. But It would do it. At least it may give you a different perspective.I hope it helps. And If there are faults please mention them.

I understand your logic (somehow), but tell me what these 2 lines of codes are supposed to do ?

Code:

  fgets(s,50,stdin);
  delete(&startptr,s);

Errors:

Code:

stru.c: In function `main':
stru.c:12: error: `s' undeclared (first use in this function)
stru.c:12: error: (Each undeclared identifier is reported only once
stru.c:12: error: for each function it appears in.)
stru.c: At top level:
stru.c:16: error: conflicting types for 'delete'
stru.c:12: error: previous implicit declaration of 'delete' was here
stru.c: In function `delete':
stru.c:40: error: syntax error at end of input

Firstly , I have written those to give you my logic. It is not compilable . That is normal that gives you some errors if you put my codes directly.

fgets takes a word from the user by keybord.

Here's my new code

Code:

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

struct elem  {
  char word [ 50 ];
  char words [50];
  struct elem * next;
  };

struct list {
  char words[50];
  struct elem *first;
  struct elem *last;
};

void init(struct list *liste)
{
  liste->first = NULL;
  liste->last = NULL;
}

void Printlist (struct elem * );

void delete(struct list *liste, struct elem *elem)
{
  struct elem *cur;
  struct elem *prev;

  if (liste->first == NULL) return;

  for (cur=liste->first, prev=NULL; cur != elem; prev=cur, cur=cur->next);

  if (prev)
    prev->next=cur->next;
  else
    liste->first=cur->next;
  if (cur->next == NULL)
    liste->last = cur;
  free(elem);
}

void mdelete(char *word, struct list *liste){
    struct elem *cur;

    for (cur=liste->first; cur != NULL; cur=cur->next)
    {
        if (strcmp(cur->word, word) == 0)
        break;
        }

        if (cur) delete(liste, cur);
}

int main ( void )
{   char words[50];
    struct list liste, *del;
    int choice;
    init(&liste);
    struct elem *start, *p;
    start = malloc ( sizeof (struct elem));
    start->next = NULL;
    del = malloc( sizeof (struct list));
    del->first = NULL;
    del->last = NULL;

do {
    printf("\n\n\t 1.  Add a word");
    printf("\n\t 2.  Delete a word");
    printf("\n\t 3.  Search for and display");
    printf("\n\t 4.  Display data in queue order");
    printf("\n\t 5.  Quit");
    printf("\n\n\t Enter your choice : ");
    scanf("&#37;i", & choice);

    if ( choice == 1 ) {
      for(p = start; p->next != NULL; p = p->next){}
        p->next = malloc (sizeof(struct elem));
        p->next->next = NULL;
        printf("\n\tEnter the word to add : ");
        scanf("%s", p->word);
     }

    if ( choice == 2 ) {
        printf("\n\tEnter the word to delete : ");
        scanf("%s", del->words);
        mdelete(del->words, &liste);
        }

    if ( choice == 4 ) {
        Printlist ( start );
        }

    } while ( choice != 5 );

return 0;
}

void Printlist (struct elem * x)
{
  int v = 1;
  while ( x->next != NULL ) {
        printf ("\n\tElement %i is : %s \n", v++, x->word);
        x = x->next;
        }
}

Could anyone help me with this code. It works and compiles but the when I enter a word to delete it doesn't work.

You're adding all your words to a elem struct list but you are trying to delete the word from a list struct list. liste is empty. So, your search of liste for the word to delete fails.