Question

So I got this task to make a program which will allow the user to enter a number of integer elements in a double-linked list and I have to delete the ones which can be divided (remainder 0) with the sum of their digits.

#include <stdio.h>
#include <stdlib.h>
#define NEW(t) (t*)malloc(sizeof(t))

typedef int info_t;

typedef struct element {
  info_t info;
  struct element *next;
  struct element *prev;
} node;

typedef node* nodep;
void insert(nodep l, info_t x) {
  nodep t = NEW(node);
  t->info=x;
  t->next=l->next;
  l->next=t;
  t->prev=l;
}
void printList(nodep l) {
  nodep t=l->next;
  while(t!=l)
  {
      printf("->%d", t->info);
      t=t->next;
  }
  printf("\n");
}
void deletedividable(nodep l) {
  nodep t=l->next;
  nodep temp;
  while(t->next!=l)
  {
      int temporary=t->info;
      int sum=0;
      while(temporary>0)
      {
          sum+=(temporary%10);
          temporary/=10;
      }
      if(!(t->info%sum))
      {
          temp=t->next;
          t->next->prev=t->prev;
          t->prev->next=t->next;
          free(t);
          t=temp;
      }
      else
        t=t->next;
   }
}

int main() {
  // declaring a leader node
  nodep list = NEW(node);
  list->next = list;
  list->prev = list;

  printf("Enter elements:\n ");
  int a;
  //if the input isn't a number the loop will exit
  while(scanf("%d", &a)) {
    //elements input function call
    insert(list, a);
  }
  // print list function call
  printList(list);
  // delete elements which are dividable with the sum of their digits

  deletedividable(list);

  printList(list);

  return 0;
}

The problem is, after the deletedividable(list); function call, nothing is printed when the second printlist is called and I can’t seem to locate the problem, some of the pointers must be getting screwed up, but I’m not sure which ones.
Any help would be much appreciated.

Answer 1

Seems an error exists in your insert() function. A hint: insertion into a circular double-linked list should set or change 4 pointers; you only set 3.