How to remove the second item from the list?

Question

It seems to be a hitch that in the "Udal" function after deleting the second element, the pointer of the first element should point to the beginning of the third. Honestly, this is a lab task. I especially need advice now.

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <conio.h> #define MAXDL 9 int h = 0; struct EL_SP { char id[MAXDL]; struct EL_SP *sled; }; void Vkl(struct EL_SP **p, char t_id[]) { struct EL_SP *pt, *k, *j; pt = (struct EL_SP *) malloc(sizeof(struct EL_SP)); strcpy(pt->id, t_id); if (*p == NULL || strcmp(pt->id, (*p)->id) < 0) { pt->sled = *p; *p = pt; } else { k = *p; while (k != NULL && strcmp(pt->id, k->id) >= 0) { j = k; k = k->sled; } j->sled = pt; pt->sled = k; } } // функция для удаления и вывода результата после комментария avp: void Udal(struct EL_SP *p) { struct EL_SP *next; int m; for( next=p, m=0; next!=NULL; next=next->sled) { m++; if (m==2) free (next); break; } } void PechSp(struct EL_SP *p) { struct EL_SP *i; printf("n Rezultat:n"); for (i = p; i != NULL; i = i->sled) puts(i->id); } void main() { struct EL_SP *p; unsigned n; unsigned i; char t_id[MAXDL]; printf("n vvedite chislo identificatorovn n="); scanf("%u", &n); getchar(); p = NULL; printf("vvedite identificatori"); printf("(posle kagdogo najimayte klavishu <ENTER>) n"); for (i = 1; i <= n; i++) { gets(t_id); Vkl(&p, t_id); } Udal(p); //здесь её вызываю PechSp(p); printf("nn Dlya zaversheniya najmite lybuyu klavishun"); getch(); }

The program is compiled without errors, but after entering the identifiers crashes.

list, look at the index, if that is necessary, delete the value
In the first element, replace sled with sled from the second.

avp avp 37.3k 3 35 90 · Accepted Answer · 2012-05-31T23:03:38

@AlexC , you are confusing work with pointers in arrays and linked lists (this is how you have it. Struct EL_SP refers to another struct EL_SP at the address in the sled field).

Check the linked lists again and change the logic for building and traversing the list.

I advise you to associate with the list 2 pointers - head (at the first in the list) and tail (at the last). For example, you can define a list like this:

 struct list { struct EL_SP *head, *tail; int list_length; };

When initializing (creating an empty list) make head = tail = NULL.

Good luck.

@avp, and if an element is suddenly added to the end of the list, then will it be necessary to correct all tails?
@insolor, apparently I wrote something incomprehensible in the answer.
It was a comment and I did not refer in detail to the data structures from the question.
For each list, the struct list has its own ( one copy per list ).
head points to the first struct EL_SP, the pointer sled ( in it ) to the next struct EL_SP, etc.
The tail of the struct list adds the last struct EL_SP in the list.

How to remove the second item from the list?

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