Thread: help with lists plz

hey im new with this all, im doing assigmnet for class, what it does it gets a list of students and their grade, splits them to fail and pass, and at the end it should each group be ordered by lexicographic order, plz help me out, i assume or the swap or the find_min or the sort r wrong, because the rest of the prog i've checked and it worked, i havent posted all the code but assumes the func that are there are working

Code:

#include <stdio.h>
#include <stdlib.h>
#include<string.h>
#define MAX_NAME_SIZE 30


typedef struct student_node
{
char name[MAX_NAME_SIZE];
double grade;
struct student_node* next;
}Student;




Student *read_students(); /*gets list of students from user*/
void print_list(Student *pHead); /*prints list of students from user*/
void split_list(Student *pHead, Student** pass, Student** fail); /*splits students list to fail&pass*/
void split_cpy_list(Student *pHead, Student** pass, Student** fail); /*splits students list to fail&pass*/
Student *sort_list(Student *pHead); /*sots students list lexicographi*/
void swap(Student *swp1, Student *swp2); /*swaps between structs*/
Student *find_min(Student *pHead); /*finds the struct where name is with smallest lexicographi*/




int main()
{
	Student *pass1=NULL, *fail1=NULL;
	Student *list = read_students();
	printf("\n");
	print_list(list);
	split_list(list, &pass1, &fail1);
	printf("\n students above 60: \n"); 
	sort_list(pass1);
	print_list(pass1);
	printf("\n students bellow 60: \n");
	sort_list(fail1);
	print_list(fail1);
	free(list);


	return 0;
}


}
void swap(Student *swp1, Student *swp2)
{
	Student *swp_tmp = NULL;
	strcpy(swp_tmp->name,swp1->name); 
	swp_tmp->grade = swp1->grade;


	strcpy(swp1->name,swp2->name); 
	swp1->grade = swp2->grade;


	strcpy(swp2->name,swp_tmp->name); 
	swp2->grade = swp_tmp->grade;
}
Student *find_min(Student *pHead)
{
    Student *tmp_find = NULL;
    tmp_find = pHead;
    while(pHead != NULL)
    {
      if(strcmp(pHead->name,tmp_find->name)<0)
      *tmp_find = *pHead;
      pHead = pHead->next;
    }
   return tmp_find;
}
Student *sort_list(Student *pHead)
{
	Student *tmp_sort = NULL;
	tmp_sort = pHead;
	while(tmp_sort != NULL)
	{
    if(strcmp(tmp_sort->name, find_min(tmp_sort->next)->name)>0)           
	swap(tmp_sort,find_min(tmp_sort->next));
	tmp_sort=tmp_sort->next;
	}
	return tmp_sort;
}

> Student *swp_tmp = NULL;
> strcpy(swp_tmp->name,swp1->name);
> swp_tmp->grade = swp1->grade;
Well until you dereference NULL anyway.

Try say

Code:

    Student swp_tmp;
    strcpy(swp_tmp.name,swp1->name);
    swp_tmp.grade = swp1->grade;

Additionally, you may want to take a look at How to define main()-FAQ