I don't even know. why does nothing work????

Assignment 10/main.c

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+/*
+ * Student: S.K. Soekhlal
+ * Number: 4860632
+ * Assignment: 5.1 + 5.2
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <limits.h>
+
+#include "salloc.h"
+#include "city.h"
+#include "road.h"
+
+#define MAX_STRING_LENGTH 50
+
+
+/*
+ * Locate city with name city_name on the map
+ */
+City *find_city (City *list_of_cities, char *city_name)
+{
+	City *c = list_of_cities;
+	while (c != NULL)
+	{
+		if (strcmp (c->name, city_name) == 0)
+			return c;
+
+		c = c->next;
+	}
+	return NULL;
+}
+
+
+/*
+ * Delete a map
+ */
+static void delete_map (City *map)
+{
+	City *map_copy;
+
+	while (map != NULL)
+	{
+		map_copy = map;
+		map = map->next;
+		delete_city (map_copy);
+	}
+}
+
+
+/*
+ * Build the map datastructure
+ */
+static City *create_map (FILE *data_file)
+{
+	int num_of_cities, i;
+    int length_of_road;
+    char city_begin[MAX_STRING_LENGTH + 1];
+    char city_end[MAX_STRING_LENGTH + 1];
+    int num_of_roads;
+    char city_name[MAX_STRING_LENGTH + 1];
+
+	City *map = NULL;
+
+	/* Read in city-names	*/
+	fscanf (data_file, "%d", &num_of_cities);
+
+	for (i = 0; i < num_of_cities; i++)
+	{
+
+		City *city;
+		City *c;
+
+		fscanf (data_file, "%s", city_name);
+
+		if (find_city (map, city_name) != NULL)
+		{
+			fprintf (stderr, "City %s already on the map\n", city_name);
+			delete_map (map);
+			exit (EXIT_FAILURE);
+		}
+
+		city = new_city (safe_strdup (city_name));
+
+		if (map == NULL)
+			/* This is the first city of the map */
+			map = city;
+		else {
+			/* Find last of city list */
+			c = map;
+			while (c->next) c = c->next;
+			/* And append new city there */
+			c -> next = city;
+		}
+	}
+
+
+
+	fscanf (data_file, "%d", &num_of_roads);
+
+	for (i = 0; i < num_of_roads; i++){
+
+        City *city;
+        Road *c;
+        Road *road;
+        Road *origin;
+        Road *destination;
+
+
+        fscanf(data_file,"%s %s %d", city_begin,city_end, &length_of_road);
+
+
+        origin = (Road*)find_city(map,city_begin);
+        destination =  (Road*)find_city(map,city_end);
+
+
+        road = new_road((City*)origin, (City*)destination, (int)length_of_road);
+
+        city = (City*)origin;
+        if (city->roads == NULL){
+			/* This is the first road of the city*/
+			city->roads = road;
+		}
+		else {
+			/* Find last of road list */
+			c = city->roads;
+			while (c->next) c = c->next;
+			/* And append new road there */
+			c -> next = road;
+		}
+	}
+
+	return map;
+}
+
+
+static void print_city_roads (City *map)
+{
+	City *city;
+	Road *road;
+
+	for (city = map; city != NULL; city = city->next)
+	{
+		printf ("Roads from city %s:\n", city->name);
+
+		for (road = city->roads; road != NULL; road=road->next) {
+			printf ("   to city %s", road->destination->name);
+			printf (" (length %d)\n", road->length);
+		}
+	}
+	free(city);
+	free(road);
+}
+
+
+static void find_shortest_roads (City *map)
+{
+
+	 char buf[MAX_STRING_LENGTH];
+	 char *destination;
+	 int length;
+	 int smallest_length;
+	 City *city;
+	 Road *road;
+
+    scanf("%s", buf);
+    city = find_city(map,buf);
+    road = city->roads;
+    smallest_length = road->length;
+    destination = road->destination->name;
+	 while(strcmp(buf,"0") != 0){
+        int a = 1;
+        city = find_city(map,buf);
+        if(road == NULL){
+            printf("There is no road from city %s\n",buf);
+        }else{
+        for (road = city->roads; road != NULL; road=road->next) {
+                if(a || road->length <= smallest_length){
+                smallest_length = road->length;
+                destination = road->destination->name;
+                a=0;/*to set smallest length to some value*/
+                }
+		/*shortest road found*/
+        }
+		length = smallest_length;
+        printf("Shortest road from city %s is to city %s: %d\n", buf, destination, length);
+	 }
+        scanf("%s", buf);
+	 }
+   	free(city);
+	free(road);
+}
+
+int main (int argc, char *argv[])
+{
+	FILE *data_file = NULL;
+	City *map = NULL;
+
+	/* Check arguments		*/
+	if (argc != 2)
+	{
+		fprintf (stderr, "Usage: %s <datafile>\n", argv[0]);
+		exit (EXIT_FAILURE);
+	}
+
+	/* Open data-file		*/
+	if ((data_file = fopen (argv[1], "r")) == NULL)
+	{
+		fprintf (stderr, "Error opening file <%s>\n", argv[1]);
+		exit (EXIT_FAILURE);
+	}
+
+	/* Create map-data-structure	*/
+	if ((map = create_map (data_file)) == NULL)
+	{
+		fprintf (stderr, "No map data found\n");
+		exit (EXIT_FAILURE);
+	}
+
+	print_city_roads (map);
+
+	find_shortest_roads (map);
+
+	/* Outit			*/
+	if (data_file != NULL)
+		fclose (data_file);
+	if (map != NULL)
+		delete_map (map);
+
+	return EXIT_SUCCESS;
+}