Thread: double linked list

I was given an assignment to write and implement a program to create a double linked list, delete, insert, find, display and reverse the contents of the double linked list.
Can any one give me ideas especially on what to put on the menu. I intend to use dynamic allocation in the functions

I think insert and delete can be futher extended .


1) insert right
2) insert left

3) delete right
4) delete right

a simple 3 node linked list may appear like this
______ _______ ________
[_|__|_] --->[_|___|_] --->[_|____|_]

Okay I get that part, now the problem here is with the reverse function. If you were me would you implement the display function that shows the list in reverse or rearrange the whole list in reverse order.

In the program I was thinking of sorting the list into e.g. alphabetical order, is that possible? I will post the code tommorrow, today I just wanted some ideas to add to my own to start with.
Before I start, in the find function, is it possible to search for a node by its contents or its always by its possition

Thanx for the site, hope its going to be very useful. Do you have any sites where i can get good code for use at school?

Thanx for the advice, gotta go for now. Will post the code tmrw, hopefully the ideas you gave me and those that i have are going to work

understand singly linked lists first,then you may be fine.also know your pointers well.

Start by creating a struct with the components that you will need for an element of a doubly linked list. Then post what you have and we can discuss it.

So far this is what I've been able to do.
Where I've quoted the code, I'm still working on that part.
I really need help on

case 1:{ //create();

and case 2://find();

How do I define the functions. I'm very confused on which values to pass into the functions and how to pass them.

#include "stdio.h"


void main()
{
int option,pstn;
struct details {
char name[25];
struct details *prev, *next;
} *start, *point, *prior;
clrscr();
start=point=prior=NULL;
do
{
printf("\n\n\t MAIN MENU\n");
printf("\n1\t Create a list");
printf("\n2\t Insert");
printf("\n3\t Delete");
printf("\n4\t Find");
printf("\n5\t Sort");
printf("\n6\t Display list");
printf("\n7\t Exit program\n\n Enter your choice\t");

scanf("%d",&option);

switch (option)
{
case 1: { //create();
char c;
start=(struct details *)malloc(sizeof(struct details));
printf("\n Name:\t\t");
scanf("%s",start->name);
prior=start;
start->prev=start->next=NULL;
printf("\n\n Press q to go back to the MAIN NENU");
if((c=getch())=='q')
break;
else
{
do
{
point = (struct details *)malloc(sizeof(struct details));
printf("\n Name\t\t\t");
scanf("%s",point->name);
prior->next = point; /* point last "next" to this record */
point->prev = prior; /* point this record's prev to prior*/
point->next = NULL; /* point this "next" to NULL */
prior = point; /* this is now the prior record */
printf("\n\n Press q to go back to the MAIN NENU");
c=getch();
} while( c != 'q' );
}
break;
}
/*case 2: { //insert(); break;
clrscr();
printf("\n\n Insert record after which position");
printf("\n\t Enter position: ");
scanf("%d",&pstn);





} */
//case 3: { delete(); break; }
case 4: { //find(); break;
int a,n;
clrscr();
if(start==NULL)
{
printf(" List is Empty ");
getch();
break;
}
printf("\n\n Find:- \n [1] Name \n [2] Node ? ");
scanf("%d",&option);
if(option==1)
{ char strng[25];


printf("\nEnter name of student that you wish to search for\n\t");
scanf("%s",strng);
point=start;
n=1;
while(point->next != NULL)
{
n++;
if(strcmp(strng,point->name)==0)
printf("[%s] found in node %d\n",point->name,n);
else if(point == NULL && strcmp(strng,point->name)!=0)
printf("No match found for \"%s\"",strng);
point=point->next;
}


getch();

}

if(option == 2)
{ point=start;

printf("\n Enter position of node");
scanf("%d",a);
if(a>=1)
{
{
for(n=1;n<=a;n++)
point=point->next;
}
//else should return NULL
printf("Node %d is \"%s\"",a,point->name);
}
else {
printf("Invalid input");
getch();
break;
}
}

}
//case 5: { sort(); break; }
//case 6: { display(); break; }
//case 7: break;
}
} while( option != 7);
printf(" The end!!!");
getch();
}

Sorry about that

Code:

 

	

		

			

			
				#include "stdio.h"


void main()
{
	int option,pstn;
	struct details 
	{
	char name[25];
	struct details *prev, *next;
	};
	
	struct details *start, *point, *prior;
clrscr();
	start=point=prior=NULL;
do
{
				printf("\n\n\t MAIN MENU\n");
				printf("\n1\t Create a list");
				printf("\n2\t Insert");
				printf("\n3\t Delete");
				printf("\n4\t Find");
				printf("\n5\t Sort");
				printf("\n6\t Display list");
				printf("\n7\t Exit program\n\n Enter your choice\t");

				scanf("%d",&option);

	switch (option)
		{
		case 1: { //create();
				char c;
				start=(struct details *)malloc(sizeof(struct details));
				printf("\n Name:\t\t");
				scanf("%s",start->name);
				prior=start;
				start->prev=start->next=NULL;
				printf("\n\n Press q to go back to the MAIN NENU");
			if((c=getch())=='q')
				break;
			else
				{
				do
				  {
      					point = (struct details *)malloc(sizeof(struct details));
					printf("\n Name\t\t\t");
					scanf("%s",point->name);
					prior->next = point;  /* point last "next" to this record */
				        point->prev = prior;   /* point this record's prev to prior*/
				        point->next = NULL;   /* point this "next" to NULL        */
				        prior = point;        /* this is now the prior record     */
					printf("\n\n Press q to go back to the MAIN NENU");
					c=getch();
				  } while( c != 'q' );
				}
				break;
			}
		
                  case 4: { //find();
				int a,n;
				clrscr();
				if(start==NULL)
					{
					printf(" List is Empty ");
					getch();
					break;
					}
				printf("\n\n Find:- \n [1] Name \n [2] Node ? ");
				scanf("%d",&option);
			if(option==1)
				{ 
			              char strng[25];
					 printf("\nEnter name of student that you wish to search for\n\t");
					 scanf("%s",strng);
					 point=start;
					 n=1;
					 while(point->next != NULL)
						 {
						 n++;
						 if(strcmp(strng,point->name)==0)
						 printf("[%s] found in node %d\n",point->name,n);
						 else if(point == NULL && strcmp(strng,point->name)!=0)
						 printf("No match found for \"%s\"",strng);
						 point=point->next;
			 			 }
						 getch();
 			       }

			else if(option == 2)
				{     
				      point=start;
					printf("\n Enter position of node");
					scanf("%d",a);
					if(a>=1)
					{
					for(n=1;n<=a;n++)
					point=point->next;
					}
					//else should return NULL
					printf("Node %d is \"%s\"",a,point->name);
				}
	    		else
				{
					printf("Invalid input");
					getch();
		 			break;
		 		}
			 }
	}
	} while( option != 7);
	printf(" The end!!!");
	getch();
}
			
		
	

Isnt the structure going to be accessible to the other functions by use of pointers?

Originally Posted by TNA$H

Isnt the structure going to be accessible to the other functions by use of pointers?

Well, yes, but a pointer to what? You can pass it as a void *, but you won't be able to access any of the members of the structures, which makes the whole thing seem extra pointless. For the function to be able to deal with a struct details, it must know what a struct details is, and for that to happen it must be able to "see" the definition of the struct (i.e., it can't be hidden inside a different function).