Thread: Linked Lists problem

alright, so heres my coding that ive come up with so far including the insert.. tell me where im completely wrong, since i am sure i am.

Code:

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

struct SLL {
   int val;
   struct SLL * next;
};

typedef struct SLL element;

int main() {
   element * curr, * head;
   int i;

   head = NULL;

   for(i=1;i<=10;i++) {
      curr = (element *)malloc(sizeof(element));
      curr->val = i;
      curr->next  = head;
      head = curr;
   }

   curr = head;

   while(curr) {
      printf("%d\n", curr->val);
      curr = curr->next ;
   }
}


void SLLinsert(shortint theID)
{
    liData *newItem = new liData;
    newItem->num = theID;
    liData *prev = NULL;
    liData *temp = NULL;
    for(temp = ptrHead; temp->ptrNext != NULL; temp = temp->ptrHead)
    {
          // is new node's priority less than current node pointer's priority?
          if(newItem->num <  temp->num)
          {
              if(prev == NULL)
              {
                    // add new node at the head
                    newItem->ptrNext = temp;
                    ptrHead = newItem;
                    break;
              }
              else
              {
                    // add new node somewhere in the middle of the list
                    newItem->ptrNext = temp;
                    prev->ptrNext = newItem;
                    break;
               }
               // save current node address
               prev = temp;
    }
     // if it gets to here then all the nodes in the list have the same
     // priority as the new node.  So i'm just adding the new node to the 
     // head of the list.
     newItem->ptrNext = ptrHead;    
    ptrHead = newItem;
}

yes no?

anyone see issues in this code? im still too new at this..

I see the missing } you speak of, and that can be fixed easily. but why don't you believe my "for" loop interates at all? am i missing something blatantly obvious?

to be honest, i never really understood what my professor was doing with liData either. But I have no idea what else I would use in place of what its doing, so I supposed I would just use it blindly

i looked through my notes back and front and couldnt find anything about his struct that he created, seems he just referred to it without really showing it...

so i thought id try and do a fresh insert with pre and post declarations just to get the idea of it down.. tell me what u think..

Code:

/* SLLinsert: inserts a new entry into the list
 * Pre conditions: The list created, not full, x is a valid list entry, p is a valid position
 * Post conditions: x has successfully been inserted into position p in list
 */

void SLLinsert(Position p, ListEntry x, List *list) {
     ListNode *newNode, *current;
     
     if (p < 0 || p > list->count)
          Error("Attempt to insert in a position not in the list.");
     else {
          newNode = MakeListNode(x);
          if (p == 0) {
               newNode->next = list->head;
               list->head = newNode;
               }
          else {
               SetPosition(p-1, list, &current);
               newNode->next = current->next;
               current->next = newNode;
               }
          list->count++;
          }
}

does that make more sense?

while waiting for assistance from you actually knowledgeable people.. :P

I decided I would try and make a flat example of how I believe the deletion would work, tell me if this also looks correct or if im missing something obvious

Code:

                                    // If the node is not the starting or the last one
void delete(int n) {      //deletes the nth position node of the linked list
     node *p;                 //node - type pointer to traverse the linked list
     int i = 1;
     while(i < n-1) {
          p = p->next;      //points to next node
          ++i;
     }
                                    //Now p is at the node previous to the node to be deleted
     node *q;                 //declares another pointer
     q = p->next;           //q is next to q
     p->next = q->next;
     free(q);
}

thanks

do the last two codings look concievable to anyone?

Your delete function will cheerfully walk off the end of the list, should you pass some very large number in for n.

where is the issue that would cause that to happen in the code?

im not recognizing where n being large would have an issue..

aside from what ive said above..

how would i throw in the exceptions for empty and repeat nodes?