Thread: Linked lists.....

This is due on Thursday (about 8 exercises) using linked lists. This is not how I have my program structured I just trimmed down eveyrthing and got it to this just to test if it would work, but it's not. On the second run instead of going in thruh the list, the information that I enter on Temp overrides what Head has. I have been trying this the whole day and could not come up with an answer. Please help. (This time I won't delete my post right away, I promise)

Code:

 
 
#include <stdio.h>
#include <stdlib.h>
typedef struct Student
{
 int x;
 char nombre[30];
 struct Student* Next;
}Student;

int main()
{
 Student *Head=NULL;
 Student *Temp;
 Student *Temp2;
 Temp=(Student*)malloc(sizeof(Student));
 Temp2=(Student*)malloc(sizeof (Student));
 int choice;
 printf("Insert Info\n");
 while (1)
 {
  printf("Press 1 to exit\n");
  scanf("%d",&choice);
  if (choice==1)
   break;
  printf("Student's Name\n");
  scanf("%s",&Temp->nombre);
  Temp->Next=NULL;
  if(Head==NULL)
   Head=Temp;
  else
  {
   Temp2=Head;
   while (Temp2->Next!=NULL)
   {
	Temp2=Temp2->Next;
   }
   Temp2->Next=Temp;
   
  
  }
 
 
 
 }
 

 return 0;
 
}

You're trying to reuse the memory for Head. This won't work very well, so you need to call malloc for each new node so that each node is unique. You'll have an easier time working with the structure when you don't have self references all over the place.

Well thank you, you were right (as always) and without further ado......my linked list....

Code:

 
 
#include <stdio.h>
#include <stdlib.h>
 typedef struct Estudiante 
 {
  char name [25];
  int age;
  struct Estudiante* Next;
  
 }Estudiante;
 
 Estudiante* AddEstudiante(Estudiante* Head)
 {
 
	 Estudiante* Fulanito;
  Estudiante* Temp;
  
  Fulanito=(Estudiante*)malloc(sizeof (Estudiante));
  Temp=(Estudiante*)malloc(sizeof (Estudiante));
  printf("Name of Student\n");
	 scanf("%s",&Fulanito->name);
	 fflush(stdin);
  printf("Age of Student\n");
  scanf("%d",&Fulanito->age);
  fflush(stdin);
	 Fulanito->Next=NULL;
  if (Head==NULL)
	 Head=Fulanito;
  else
  {
   Temp=Head;
  while (Temp->Next!=NULL)
  {
   Temp=Temp->Next;
  }
  Temp->Next=Fulanito;   
   
  }
 
  return Head;
 }

 void ViewList(Estudiante* Head)
 {
  Estudiante* Temp;
  Temp=(Estudiante*)malloc(sizeof (Estudiante));
  Temp=Head;
   
 
  while(1)
  {
  printf("\nName of Student %s",Temp->name);
  printf("\nAge of Student %d\n",Temp->age);
  if (Temp->Next==NULL)
   break;
  Temp=Temp->Next;
  }
   
 
 }
 
 
  int DeleteStudent(Estudiante* Head)
 {
  if (Head==NULL)
  {
   printf("\nList is empty\n");
   return 1;
  }
  
  Estudiante* Temp;
  Estudiante* Temp2;
  Temp=(Estudiante*)malloc(sizeof (Estudiante));
  Temp2=(Estudiante*)malloc(sizeof (Estudiante));
  Temp=Head;
  while (Temp->Next!=NULL)
  {
   Temp2=Temp;
   Temp=Temp->Next;
  }

  delete Temp;
  Temp2->Next=NULL;
  
  
	 
  return 0;
  
 }
 
 
 
int main()
{
 int choice=0;
 bool Done=false;
 
 
 Estudiante* Head;
 Head=NULL;
 

 for (;;)
 {
  printf("\nWhat would you like to do\n");
  printf("1)Insert student\n");
  printf("2)View List\n");
  printf("3)Delete Student\n");
  printf("4)Quit\n");
  scanf("%d",&choice);
  fflush(stdin);
  switch (choice)
  {
  case 1: Head=AddEstudiante(Head);
	
	  
	  break;
  case 2:    
	   ViewList(Head);
	   break;
  case 3: DeleteStudent(Head);
	break;
 
  case 4: Done=true;
	break;
  }
  if (Done)
   break;
 }
 
 

 return 0;

}

>fflush(stdin);
Bad.

>delete Temp;
This is C. That line shouldn't even compile. Also, I don't see where you free() all of the memory you allocated in the program.

Originally Posted by XSquared

>fflush(stdin);
Bad.

>delete Temp;
This is C. That line shouldn't even compile. Also, I don't see where you free() all of the memory you allocated in the program.

Well it does, and I didn't really notice it until now, as you can probably guess I am more used to C++.

About that memory freeing stuff, that would be on my todo list. I also checked for the list being empty and people trying to delete stuff while it's empty, but it's not posted on there.

Code:

int DeleteStudent(Estudiante* Head)
 {
  if (Head==NULL)
  {
   printf("\nList is empty\n");
   return 1;
  }
  
  Estudiante* Temp; // Not C!
  Estudiante* Temp2; // Not C!
  Temp=(Estudiante*)malloc(sizeof (Estudiante));
  Temp2=(Estudiante*)malloc(sizeof (Estudiante));
  Temp=Head;
  while (Temp->Next!=NULL)
  {
   Temp2=Temp;
   Temp=Temp->Next;
  }

  delete Temp; // Not C!

Unless you're using C99 (unlikely), you cannot declare variables except a the beginning of a block. And delete is not an operator that frees memory in C.

>bool Done=false;
Unless you're using C99, C does not have a bool type. I get the distinct feeling that you are trying to write C but compiling as C++. This is hiding a lot of the legitimate C errors that you would get.

I get the distinct feeling that you are trying to write C but compiling as C++. This is hiding a lot of the legitimate C errors that you would get.

Oops.........and you'd be right...I guess college professor would not like that.......need to change that.