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station.c
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station.c
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// station.c -- simulates a doubly-linked list of TTC stations
// Farhang Tarlan, winter 2013
#include "ttc.h"
#define MAX_SIZE 20
struct station* make_station(char *name, int pos)
{
// Creates a new station node in our doubly-linked list, setting its name and position to name and pos.
// The new node is unlinked (prev and next are both NULL).
// PRE: none
// POST: none
struct station *new_node = (struct station*) malloc(sizeof(struct station));
new_node->name = (char *) malloc((strlen(name) + 1) * sizeof(char));
strcpy(new_node->name, name);
new_node->pos = pos;
new_node->next = NULL;
new_node->prev = NULL;
new_node->passengers = NULL;
return new_node;
}
int passengers_at_station(struct station *curr_station)
{
// Number of passengers waiting at a given station, curr_station. If station == NULL, returns 0.
// PRE: none
// POST: none
if(curr_station)
{
return num_passengers(curr_station->passengers);
}
return 0;
}
void print_station(struct station *current)
{
// Prints a single station. If current == NULL, prints "No station. \n".
// PRE: none.
// POST: none
if(!current)
{
printf("No station. \n");
}
else
{
if(current->prev)
{
printf("%13s -> ", current -> prev -> name);
}
else
{
printf(" ");
}
printf("%s (%d)", current -> name, num_passengers(current -> passengers));
if(current->next)
{
printf("-> %-13s \n", current -> next -> name);
}
else
{
printf("\n");
}
}
}
void print_stations(struct station *first)
{
// Prints all stations in a linked list
// PRE: none
// POST: none
printf("\nThe stations: \n");
struct station *curr = first;
while(curr)
{
print_station(curr);
curr = curr -> next;
}
}
void insert_station_after(struct station *node, struct station *new_node)
{
// inserts a new station new_node after node, linking node into the doubly-linked list.
new_node -> next = node -> next;
new_node -> prev = node;
node -> next = new_node;
if (new_node -> next)
(new_node -> next) -> prev = new_node;
}
struct station* read_stations()
{
// reads the file bloor_line.txt, converts each line into a doubly-linked list of stations
char name[MAX_SIZE];
int pos, i = 0;
struct station* prev = NULL;
struct station* new_station = NULL;
struct station* first;
FILE* fop = fopen("bloor_line.txt", "r");
// looping through the text file line by line
while (fscanf(fop, "%s %d\n", name, &pos) != EOF)
{
// creating the first station node saving a pointer that points to the first node in the linked list
if (i == 0)
{
new_station = make_station(name, pos);
first = new_station;
}
// linking every other node correctly in its place in the linked list
else
{
prev = new_station;
new_station = make_station(name, pos);
insert_station_after(prev, new_station);
}
i += 1;
}
fclose(fop);
return first;
}
void add_passenger(struct station *curr_station)
{
// adds a new passenger to the station curr_station
struct passenger* new_passenger = make_passenger();
new_passenger -> next = curr_station -> passengers;
curr_station -> passengers = new_passenger;
}
void add_n_passengers(struct station *curr_station, int n)
{
// adds n passengers to the station curr_station
int i;
for (i = 0; i < n; i += 1)
{
add_passenger(curr_station);
}
}
int total_passengers(struct station *first)
{
// returns the total number of passengers at all stations in the linked list pointed to by first
struct station* curr;
int num = 0;
int total = 0;
// looping through the linked list of stations, calling num_passengers to calculate the number of passengers at each station
for (curr = first; curr != NULL; curr = curr -> next)
{
num = num_passengers(curr -> passengers);
total += num;
}
return total;
}
double average_wait_time(struct station *first)
{
// returns the average wait time of all the passengers at all the stations in the linked list pointed to by first
int num = 0;
double wait = 0.0;
struct station* curr;
struct passenger* pass;
for (curr = first; curr != NULL; curr = curr -> next)
{
for (pass = curr -> passengers; pass != NULL; pass = pass -> next)
{
num += 1;
wait += pass -> waiting;
}
}
return (wait / num);
}
struct station* get_station_at_pos(int position, struct station *first)
{
// returns the station located at the position given by position, NULL if a station is not found.
if (first == NULL)
{
return NULL;
}
if (first -> pos == position)
return first;
return get_station_at_pos(position, first -> next);
}
void remove_all_stations(struct station **first)
{
// removes and frees the memory of all the stations in the linked list beginning with first.
struct station* curr_station = *first;
struct passenger* curr_passenger;
// looping through stations:
while (curr_station != NULL)
{
free(curr_station -> name);
// freeing the passenger list by calling clear_passenger_list
curr_passenger = curr_station -> passengers;
clear_passenger_list(&curr_passenger);
// freeing the statoin itself
curr_station = curr_station -> next;
free(*first);
*first = curr_station;
}
}