Question

Here’s my code so far:

struct stockRecord {
  int code;
  char name[MAXNAMELEN];
  struct stockRecord* next;
};

struct stockRecord* temp = NULL;
struct stockRecord* head = NULL;
struct stockRecord* prevptr = NULL;

struct stockRecord* resfun(struct stockRecord* list)
{
   temp = list;
   if (head == NULL) head = list;
   if (temp == NULL) {
      return head;
   } else {
      if (prevptr == NULL) {  //first node
         if (strstr(temp->name, "ABC-") != NULL) {
            temp = temp->next;  //remove the current node
         }
      }
      prevptr = list;

      if (temp->next == NULL) {
         return head;
      } else {
         return resfun(temp);
      }
   }
}

I don’t know how to remove a node, and re-link the neighbour nodes. Then I’ll need to return the head node to the main function.

Please can anyone help?

Thanks.

Answer 1

Vega,

To remove the first element from a single-linked-list, all you really need to do is “forget” the first element (the head).

The general procedure for removing the first node is:

1. if nodes are dynamically allocated
   (which they almost allways are in a
   linked-list) then free the memory
   allocated to this node.
2. “forget” the head by moving it “down” one. I allways think of a linked-list as dot-points going DOWN the page.

The general procedure for removing a node in the middle of a list is:

1. free memory
2. link the entry above this one to one below this one.
   • I.e. prev->next = this->next

The general procedure for removing the last node is (I bet you can guess):

1. free memory
2. prev->next = null; (where prev is the second last node)

Recursion has nothing to do with it.

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

    #define SIZE_OF_NAME 12
    #define SUCCESS 0

    typedef struct Stock* stock;

    struct Stock {
      int code;
      char name[SIZE_OF_NAME];
      stock next;
    };

    stock head = NULL;
    stock prev = NULL;

    stock StripABC(stock curr)
    {
      if (strstr(curr->name, "ABC-") != NULL) {
        // the first name contains "ABC-", so strip it.
        head = head->next;
        curr = head;
      }
      return head;
    }

    int main(int argc, char *argv[])
    {
      struct Stock a, b;
      a.code = 1; strcpy(a.name, "ABC-");
      b.code = 2; strcpy(b.name, "Widget");
      head = &a;
      head->next = &b;

      StripABC(head);

      printf("head->name: %s\n", head->name);

      return SUCCESS;
    }

Good luck with it. BTW, linked lists are STILL “stock in trade” for ansi-c programmers. I still work with them far too often 😉

Cheers. Keith.