Sorted List

Sorted List

[Nanakos Chrysostomos]

Hi ,all.Can someone please explain this source code with an example???

***********************************************************************
#include <stdio.h>

typedef struct list_tag {
        int data;
        struct list_tag *next;
}ListNode;

typedef ListNode *slist;
slist empty = NULL;

void slistInsert(slist *sp,int t)
{
        ListNode *n=(ListNode *)malloc(sizeof(ListNode));
        if(n == NULL)
        {
                printf("Out of memory\n");
                exit(1);
        }
        n->data = t;
        while(*sp!=NULL && (*sp)->data < t)
        {
        sp = &((*sp)->next);   //Why we do this here,i miss this point
        }
        n->next = *sp;
        *sp = n;

}


void slistRemove(slist *sp,int t)
{
        ListNode *n;
        while(*sp!=NULL && (*sp)->data <t)
                sp = &((*sp)->next);
        if(*sp == NULL)
        {
                printf("Not found\n");
                exit(1);
        }

        n=*sp;
        *sp = (*sp)->next;
        free(n);
}

void slistPrint(slist s)
{
        ListNode *n;
        for(n=s;n!=NULL; n=n->next)
                printf("%d\n",n->data);
}

void main()
{

      slistInsert(&empty,4);
      slistInsert(&empty,8);

      slistInsert(&empty,24);
      slistInsert(&empty,50);
      slistInsert(&empty,20);
      slistInsert(&empty,2);
      slistRemove(&empty,4);
      slistInsert(&empty,18);
      slistPrint(empty);
}

Thank you very much in advance.

Re: Sorted List

[Bharat Jain]

After the while loop "sp" would be containing the address of the node 
after
 which the new node is to be inserted.
 
 It is done in this way because *sp = *sp->next would modify the global
 "empty" pointer which we dont want. "empty" should always point to
 first element of the list.  
 
 Hope this helps.