Data struct question

I'm writing a program which organizes a buses network.
these are the structs I use:

Code:

typedef struct lns{
	int num;
	struct lns *nextline;
}lns;

typedef struct stns{
	int code;
	struct stns *nextstn;
}stns;


typedef struct {
	int num;
	stns *stations;
	
}LINE;

typedef struct {
	int SNcode;
	int CTcode;
	char city[30];
	char adress[30];
	lns *lines;
}STATION;

I have some functions that fill some data in structures.
Now, I got a function which ask for a station code & determine which lines pass this station.

Code:

FindLines (LINE *L)
{
	int i=0, orgn, dest;
	puts ("\nEnter origin station code first and destination station code second");
	flushall();
	scanf ("%d %d", &orgn, &dest);
		while (L[i].stations->code && i<STN)
		{
			if (orgn==L[i].stations->code)
			{
				L[i].stations=L[i].stations->nextstn;
				while (L[i].stations->code)
					{
						if (dest==L[i].stations->code)
						{
							printf ("line %d pass origin code %d station & destination code %d station", L->num, orgn, dest);
							break;
						}
						else 
							puts ("No match found");
					}
			}
		L[i].stations=L[i].stations->nextstn;
		i++;
		}
}

When I run it I get infenite output of "No match found", though my input has positive data.
Debugger shows I got stuck in last iteration of the top while loop, I think, with a memory allocation error.
Help will be highly epriciated!

Ronen

> while (L[i].stations->code)
Since nothing inside the loop changes this, it is a constant and therefore true all the time.

Set a temporary pointer, and follow the list with something like
temp = temp->nextstn;

This is my modified function, as I understood your offer:

Code:

FindLines (LINE *L)
{
	int i=0, orgn, dest;
	LINE *temp;
	temp=L;
	puts ("\nEnter origin station code first and destination station code second");
	flushall();
	scanf ("%d %d", &orgn, &dest);
		while (temp[i].stations->nextstn && i<STN)
		{
			if (orgn==temp[i].stations->code)
			{
			
				while (temp[i].stations->nextstn)
					{
						temp[i].stations=temp[i].stations->nextstn;
						if (dest==temp[i].stations->code)
						{
							printf ("line %d pass origin code %d station & destination code %d station", temp->num, orgn, dest);
							break;
						}
						else 
							puts ("No match found");
					}
			}
		L[i].stations=L[i].stations->nextstn;
		i++;
		}
}

I'm still stuck in the same place with same responds:
Unhandled exception in "filename" access violation

Code:

temp = line;
while ( temp ) {
  // some stuff
  temp = temp->next;
}

only when I put
>while (i<STN)
in first loop, can function work.
didn't manage to find any other solution to it.

Code:

FindLines (LINE *L)
{
	int i=0, orgn, dest;
	LINE *temp;
	temp=L;
	puts ("\nEnter origin station code first and destination station code second");
	flushall();
	scanf ("%d %d", &orgn, &dest);
		while (i<STN)
		{
			if (orgn==temp[i].stations->code)
			{
			
				while (temp[i].stations->nextstn)
					{
						temp[i].stations=temp[i].stations->nextstn;
						if (dest==temp[i].stations->code)
						{
							printf ("line %d pass origin code %d station & destination code %d station", temp->num, orgn, dest);
							break;
						}
						else 
							puts ("No match found");
					}
			}
		temp[i].stations=temp[i].stations->nextstn;
		i++;
		}
}