My first and probably last LINKED LIST! - Please help

[Mandy_C]

Hi everyone,

I'm new to this site and also a beginner at C programming, I was wondering if anyone could help me with this problem that I have involving a linked list.

I always get a 'bus error' when I try to access the data in the structure and I don't know what I have done wrong.

Here is my code so far:

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

struct node
{
	char depart;
	char arrive;
	int depart_time;
	int arrive_time;
	
	struct node *next;
};

struct node* mknode(char depstat, char arrstat, int dtime, int atime)
{
	struct node* np;
	
	np=(struct node*)malloc(sizeof(struct node));
	
//	if(np)
//	{
		np -> depart=depstat;
		np -> arrive=arrstat;
		np -> depart_time=dtime;
		np -> arrive_time=atime;
		
		np -> next=NULL;
//	}
	
	return np;
}

int main(void)
{
	int hours_a, minutes_a,c=0,d=0,start=0,check=1;
	char arrive[20],depart[20],a[25],b[25];
	FILE *ttimes;
	struct node *n,*n_start,*n2;
		
	ttimes=fopen("times.txt","r");
	if(ttimes == NULL)
	{
		printf("There was an error opening the train timetable\nNow exitting...\n");
		
		return 1;
	}
	
	printf("Enter the name of the station you will be departing from:\n");
	scanf("%s", depart);
	
	printf("Enter the name of the station you will be arriving at:\n");
	scanf("%s", arrive);
	
	printf("****ARRIVE: %s****\n****DEPART: %s****\n", arrive, depart);
	
	printf("Please enter the time (HH MM) at which you would like to arrive at %s:\n", arrive);
	scanf("%d %d", &hours_a, &minutes_a);
	
	printf("****ARRIVE: %d:%d\n", hours_a, minutes_a);
	
	while(fscanf(ttimes,"%s %s %d %d",a,b,&c,&d) != EOF)
	{
		if(check==1)
		{
			printf("++++++++++\n");
			n_start=n;
		}
		if(start == 0)
		{	
//			printf("AAA\n");
			n=mknode(a,b,c,d);
			start=1;
		}
		if(start == 1)
		{	
//			printf("BBB\n");
			n2=mknode(a,b,c,d);
			n->next=n2;
			n=n2;
//			printf("B2B\n");
//			start=0;
		}	
		
		printf("CHECK #%d:: A=%s,B=%s,C=%d,D=%d\n",check,a,b,c,d);
		printf("NODES #%d:: A=%s,B=%s,C=%d,D=%d\n",check,n->depart,n->arrive,n->depart_time,n->arrive_time);
		
		check++;
	}
	
	printf("***EXITED SCANF***\n");
	
	fclose(ttimes);

	return 0;
}

Note - I have used alot of printf's for testing the program when I run it.


As you can see I'm struggling, any help would be greatly appreciated. Thank you.

Mandy

[Salem]

I'd be amazed if this even compiles, never mind runs

> n=mknode(a,b,c,d);
a and b are strings, yet the function only expects char.


As well as a mknode() function, also write
struct node* appendList ( struct node *head, struct node *newNode );

> struct node *n,*n_start,*n2;
Initialise these to NULL for a proper empty list.

[cdalten]

Here is what I got.

$gcc --version
gcc (GCC) 3.3.3 (SuSE Linux)
Copyright (C) 2003 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$gcc -Wall ll.c -o lc
ll.c: In function `main':
ll.c:72: warning: passing arg 1 of `mknode' makes integer from pointer without a cast
ll.c:72: warning: passing arg 2 of `mknode' makes integer from pointer without a cast
ll.c:78: warning: passing arg 1 of `mknode' makes integer from pointer without a cast
ll.c:78: warning: passing arg 2 of `mknode' makes integer from pointer without a cast
ll.c:86: warning: format argument is not a pointer (arg 3)
ll.c:86: warning: format argument is not a pointer (arg 4)
$./lc
There was an error opening the train timetable
Now exitting...
$

[Mandy_C]

Thank you for your help Salem, i have corrected the function to expect a char array character array. btu i still am unable to get the information from the linked list. when the program runs the n->depart etc it always crashes.

i have absolutley no clue what is wrong the data is read in using fscanf from a file, the file is the correct format to read in the data but i just cant get the data back from the structure

any assistance would be great. thank you.

[Salem]

> char depart;
Say
char depart[50];

> np -> depart=depstat;
Say
strcpy(np -> depart, depstat );

And pass the first two parameters as char* rather than char.

Post your latest attempt if you still can't figure it out with those changes.
You should be pretty close to the answer...

[Mandy_C]

Thats awesome thank you sooo much

this part of the program is working good now

thanks a lot!!!