Dynamic allocation problem with linked lists

[gruba]

Homework Statement

I need to create data structure which contains three linked lists that are connected to one root node.

Homework Equations

-Data structures

The Attempt at a Solution

I can't find what is wrong with the following code:

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

typedef struct node
{
  struct node *next;
  int y;
}NODE;

typedef struct root
{
  struct node *first;
  struct node *middle;
  struct node *last;
  int x;
}ROOT;

ROOT *form_root(int x)
{
  ROOT *new_root=(ROOT *)malloc(sizeof(ROOT));
  new_root->first=new_root->middle=new_root->last=0;
  new_root->x=x;
  return new_root;
}

void add_in_list(NODE *list,int y)
{
  NODE *new_node=(NODE *)malloc(sizeof(NODE));
  new_node->y=y;
  new_node->next=NULL;
  if(list == 0)
  list=new_node;
  else
  return ;
}

ROOT *add(ROOT *root,int x)
{
  if(root==0)
  return form_root(x);
  if(x < root->x)
  add_in_list(root->first,x);
  else
  if(x > root->x)
  add_in_list(root->last,x);
  else
  add_in_list(root->middle,x);
  return root;
}

int erase_from_list_(NODE *node,int y)
{
  NODE *p=node->next;
  if(p==0)
  return 0;
  node->y=p->y;
  node->next=p->next;
  free(p);
  return 1;
}

ROOT *erase(ROOT *root, int x)
{
  if(root==0)
  return 0;
  else if(x < root->x)
  root->first=erase_from_list_(root->first,x);
  else if(x > root->x)
  root->last=erase_from_list_(root->last,x);
  else if(x==root->x)
  root->middle=erase_from_list_(root->middle,x);
  else
  return 0;
  return root;
}

void sort_list(NODE *head)
{
  for(;head && head->next;head=head->next)
  {
  NODE *min=head,*p;
  for(p=head->next;p;p=p->next)
  if(min->y > p->y)
  min=p;
  if(min!=head)
  {
  int temp=head->y;
  head->y=min->y;
  min->y=temp;
  }
  }
}

void sort(ROOT *root)
{
  sort_list(root->first);
  sort_list(root->middle);
  sort_list(root->last);
}

void print_list(NODE *head)
{
  while(head)
  {
  printf("%d",head->y);
  head=head->next;
  }
}

void print(ROOT *root)
{
  print_list(root->first);
  print_list(root->middle);
  print_list(root->last);
}

int main()
{
  ROOT *root=0;
  int array[][3]={{0,1,2},{3,4,5},{12,7,8}};
  int i;
  for(i=0;i<3;i++)
  root=add(root,*array[i]);
  int num;
  printf("enter the number to be removed:");
  scanf("%d",&num);
  root=erase(root,num);
  sort(root);
  NODE *head=0;
  print(head);
  return 0;
}

Could someone help?

 

[Mark44]

Homework Statement

I need to create data structure which contains three linked lists that are connected to one root node.

Homework Equations

-Data structures

The Attempt at a Solution

I can't find what is wrong with the following code:
<omitted>

Could someone help?

A clue as to what's wrong would be helpful. Does your code compile? If not, what compiler and/or linker errors are you getting (including the line number where the error occurs)? Does your code compile, but produce run-time errors? Does your code run, but produce incorrect results?

We're happy to help, but please give us some information to go on.

 

[STEMucator]

Just looking at this function:

ROOT *form_root(int x)
{
  ROOT *new_root=(ROOT *)malloc(sizeof(ROOT));
  new_root->first=new_root->middle=new_root->last=0; ********* Really look at this line.
  new_root->x=x;
  return new_root;
}

Can you see why your code is wrong? It should read like so:

ROOT *new_root = (Insert a new root here);
new_root->first = (Insert a new node here);
new_root->second = (Insert a new node here);
new_root->third = (Insert a new node here);
new_root->x = x;

The first, second and third fields are not integers you can set to zero. They are actually nodes with a next and y field.

Look at your code more.

 

[Mark44]

Just looking at this function:

ROOT *form_root(int x)
{
  ROOT *new_root=(ROOT *)malloc(sizeof(ROOT));
  new_root->first=new_root->middle=new_root->last=0; ********* Really look at this line.
  new_root->x=x;
  return new_root;
}

Can you see why your code is wrong? It should read like so:

ROOT *new_root = (Insert a new root here);
new_root->first = (Insert a new node here);
new_root->second = (Insert a new node here);
new_root->third = (Insert a new node here);
new_root->x = x;

The OP's first line of code uses malloc() to allocate heap memory for a new node. This is the appropriate thing to do, not "insert a new root here" as you wrote.

The first, second and third fields are not integers you can set to zero. They are actually nodes with a next and y field.

Correct, they are not integers, but the OP is initializing these pointers to NULL What the OP has done is not the best way to do things, but I get what the intent is.

Look at your code more.

This is also good advice for you, @Zondrina.

I'm waiting for the OP to give us more information about what is wrong with the posted code.