Double linked list - C - c

Question

I'm trying to make a simple double linked list, I used (switch) in the first place:
int choice, data;
switch(choice)
{
case 1:
printf("Enter Your Data\n");
scanf("%d",&data);
InsetFirst(data);
data =0;
break;
case 2:
printf("Enter Your Data\n");
scanf("%d",&data);
InsertLast(data);
data =0;
break;
case 3:
printf("The list from the beginning to the End :\n");
PrintForward();
break;
case 4:
printf("The list from the end to the beginning\n");
PrintBackward();
break;
case 5:
printf("Enter the data you want search\n");
scanf("%d",data);
Search(data);
if(Search(data))
{
printf("%d\n",*(Search(data)));
}
else
{}
data =0;
break;
case 6:
printf("Enter The data you want to delete\n");
scanf("%d",&data);
DeleteNode(data);
break;
default :
printf("Not Valid Entry\n");
But it kept showing me this error in one of the functions
"expected declaration or statement at end of input"
knowing that I tested the functions individually and it worked properly,
After that I used (if,if-else) and then it worked`
int main()
{
int choice=1 , data;
while (1)
{
printf("Choose from the following options\n\n");
printf("1-Insert at the beginning\n2-Append\n3-Print Forward\n4-Print Backward\n5-Search\n6-Delete\n");
scanf("%d",&choice);
if(choice==1)
{
printf("Enter Your Data\n");
scanf("%d",&data);
InsetFirst(data);
data =0;
}
else if (choice==2)
{
printf("Enter Your Data\n");
scanf("%d",&data);
InsertLast(data);
data =0;
}
else if(choice==3)
{
printf("The list from the beginning to the End :\n");
PrintForward();
}
else if(choice==4)
{
printf("The list from the end to the beginning\n");
PrintBackward();
}
else if(choice==5)
{
printf("Enter the data you want search\n");
scanf("%d",data);
Search(data);
data =0;
}
else if(choice==6)
{
printf("Enter The data you want to delete\n");
scanf("%d",&data);
DeleteNode(data);
}
else
{
printf("Enter a Valid Choice\n");
}
}`,
but there were error with search function in case the item doesn't exist.
hope anyone can help me, thanks in advance, peace :)
here is the full code with commented sections that don't work:
#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
struct Node
{
int data;
struct Node* pnext;
struct Node* pprev;
};
struct Node* pstart = NULL;
struct Node* plast = NULL;
/** Functions Prototype **/
struct Node* CreatNode (void);
void InsetFirst (int data);
void InsertLast (int data);
void PrintForward (void);
void PrintBackward (void);
struct Node* Search (int data);
void DeleteNode (int Node );
int main()
{
int choice=1 , data;
while (1)
{
printf("Choose from the following options\n\n");
printf("1-Insert at the beginning\n2-Append\n3-Print Forward\n4-Print Backward\n5-Search\n6-Delete\n");
scanf("%d",&choice);
if(choice==1)
{
printf("Enter Your Data\n");
scanf("%d",&data);
InsetFirst(data);
data =0;
}
else if (choice==2)
{
printf("Enter Your Data\n");
scanf("%d",&data);
InsertLast(data);
data =0;
}
else if(choice==3)
{
printf("The list from the beginning to the End :\n");
PrintForward();
}
else if(choice==4)
{
printf("The list from the end to the beginning\n");
PrintBackward();
}
else if(choice==5)
{
printf("Enter the data you want search\n");
scanf("%d",data);
Search(data);
data =0;
}
else if(choice==6)
{
printf("Enter The data you want to delete\n");
scanf("%d",&data);
DeleteNode(data);
}
else
{
printf("Enter a Valid Choice\n");
}
}
/*
int choice,data;
switch(choice)
{
case 1:
printf("Enter Your Data\n");
scanf("%d",&data);
InsetFirst(data);
data =0;
break;
case 2:
printf("Enter Your Data\n");
scanf("%d",&data);
InsertLast(data);
data =0;
break;
case 3:
printf("The list from the beginning to the End :\n");
PrintForward();
break;
case 4:
printf("The list from the end to the beginning\n");
PrintBackward();
break;
case 5:
printf("Enter the data you want search\n");
scanf("%d",data);
Search(data);
if(Search(data))
{
printf("%d\n",*(Search(data)));
}
else
{}
data =0;
break;
case 6:
printf("Enter The data you want to delete\n");
scanf("%d",&data);
DeleteNode(data);
break;
default :
printf("Not Valid Entry\n");
*/
return 0;
}
/** Function to create Node in the list **/
struct Node* CreatNode (void)
{
struct Node* temp;
temp = (struct Node*) malloc(sizeof(struct Node));
if (!temp)
{
printf("\nNot Enough Memory");
}
else
{
return temp;
}
}
/**************************************************************************************/
/** Function to Insert Node at the Beginning of the list **/
void InsetFirst (int data)
{
struct Node* temp;
temp = CreatNode();
temp ->data = data;
temp ->pnext = NULL;
temp ->pprev = NULL;
if (pstart == NULL)
{
pstart = temp;
plast = temp;
}
else
{
temp ->pnext = pstart;
pstart ->pprev =temp;
pstart = temp;
}
}
/***********************************************************************************/
/** Function to Insert Node at the End of the List **/
void InsertLast (int data)
{
struct Node* temp;
temp = CreatNode();
temp ->data = data;
temp ->pnext = NULL;
temp ->pprev = NULL;
if (pstart == NULL)
{
pstart = temp;
plast = temp;
}
else
{
temp ->pprev = plast;
plast ->pnext = temp;
plast = temp;
}
}
/**********************************************************************************************/
/** Function to Print the list From the beginning to the End **/
void PrintForward (void)
{
struct Node* current;
current = pstart;
printf("\nThe list From the Beginning to the End :\n");
while (current)
{
printf("\n%d",current->data);
current = current->pnext;
}
printf("\n");
}
/*********************************************************************************************/
void PrintBackward (void)
{
struct Node* current;
current = plast;
printf("\nThe list From End to the Beginning :\n");
while (current)
{
printf("\n%d",current->data);
current = current->pprev;
}
printf("\n");
}
/*********************************************************************************************/
/** Function To Find a Given Data **/
struct Node* Search (int data)
{
struct Node* current;
current = pstart;
if (current)
{
while(current)
{
if (current->data == data)
{
return current;
}
current = current->pnext;
}
printf("\nIt's not found\n");
return NULL;
}
}
/**************************************************************************************/
/** Function to Delete a Given Node **/
void DeleteNode (int Node )
{
struct Node* state;
state = Search(Node);
if (state)
{
if ((state == pstart) && (state == plast))
{
pstart = NULL;
plast = NULL;
}
else if (pstart == state)
{
pstart = state->pnext;
state->pnext->pprev = NULL;
}
else if (plast == state)
{
plast = state->pprev;
state->pprev->pnext = NULL;
}
else
{
state->pprev->pnext = state->pnext;
state->pnext->pprev = state->pprev;
}
free(state);
}
else
{
printf("NOT Found\n");
}
}

Answer 1

There was a few problems in your code. I was working with the switch version, and there were also problems with the if else version.
case 5:
printf("Enter the data you want search\n");
scanf("%d",data);
Search(data);
if(Search(data))
{
printf("%d\n",*(Search(data)));
}
else
{}
data =0;
break;
When you use scanf you need to send a pointer to the location where you want to store something, so it will be scanf("%d", &data). Also printf's %d needs int value as argument but here:
printf("%d\n",*(Search(data)));
you are sending it a Node, and so it will not accept it. You need to send the data that is within the Node so you do this:
printf("%d\n",(*(Search(data))).data);
And you don't need to have else with an empty block, if you remove it it won't affect the program.
Now we have a problem in the CreatNode function which does not return anything in the case temp is null. So you need to return null in the if block in case there was not enough memory:
struct Node* CreatNode (void)
{
struct Node* temp;
temp = (struct Node*) malloc(sizeof(struct Node));
if (!temp)
{
printf("\nNot Enough Memory");
return NULL; //YOU NEED TO RETURN NULL HERE
}
else
{
return temp;
}
}
Function Search won't return anything if for example first current equals NULL, so you need to move return and printf line out of if block like this:
struct Node* Search (int data)
{
struct Node* current;
current = pstart;
if (current)
{
while(current)
{
if (current->data == data)
{
return current;
}
current = current->pnext;
}
}
printf("\nIt's not found\n");
return NULL;
}
And the last thing and the reason why your switch does not work is because it is not in a loop. Switch by itself is not a loop so you need to put it in a while loop that works until for example, user enters 0. So this will be a solution:
int main()
{
int choice=-1,data;
while(choice != 0)
{
printf("\n\nChoose from the following options\n\n");
printf("1-Insert at the beginning\n2-Append\n3-Print Forward\n4-Print Backward\n5-Search\n6-Delete\n");
scanf("%d", &choice);
switch(choice)
{
case 1:
/*...*/
case 2:
/*...*/
case 3:
/*...*/
case 4:
/*...*/
case 5:
/*...*/
case 6:
/*...*/
case 0:
break;
default :
printf("Not Valid Entry\n");
}
}
return 0;
}