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Marc
359
OU4/is_connected.c
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359
OU4/is_connected.c
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#include <stdio.h>
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#include <stdbool.h>
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#include <stdlib.h>
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#include <graph.h>
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#include <ctype.h>
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#include <queue.h>
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#include <dlist.h>
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#include <string.h>
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#define MAXNODENAME 40
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#define BUFSIZE 400
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/*
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* is:connected.c: The main program for traversing a graph for "Obligatorisk uppgift 4" in the "Datastructures and
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* algorithms" course at the Department of Computing Science, Umea University.
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*
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* Authors: Ellen Horneij tfy22ehj
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* Jakob Nyström tfy22jnm
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* Marc Meunier tfy22mmr
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*
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* Version information:
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* v1.0 2025-05-25: First public version.
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* v2.0 2025-06-02: Fixed traversing
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* v3.0 2025-07-29: Fixed error messages
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*
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*/
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// ===========HELP FUNCTIONS ============
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/**
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* @brief Find position of first non-whitespace character.
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*
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* @param s - string to search.
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* @return int - Returns the position of the first non-whitespace character, or -1 if not found.
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*/
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int first_non_white_space(const char *s)
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{
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int i = 0; // Start at first char.
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// Advance as long as we're loooking at white-space until we hit EOL.
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while (s[i] && isspace(s[i]))
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{
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i++;
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}
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// We found a non-whitespace char.
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if (s[i])
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{
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// It was a proper characted. Return its position.
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return i;
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}
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else
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{
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// It was the null terminator. Return fail.
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return -1;
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}
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}
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/**
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* @brief Determine if the string is blank.
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*
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* @param s - string to search.
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* @return true if the line contains only whitespace chars.
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* @return false if the line contains at least one non-whitespace char.
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*/
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bool line_is_blank(const char *s)
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{
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// Line is blank if it only contained white-space chars.
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return first_non_white_space(s) < 0;
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}
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/**
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* @brief Determine if the string is a comment line.
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*
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* @param s - string to search.
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* @return true if the line is a comment line.
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* @return false if the line is not a comment line.
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*
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* A comment line has a hash sign '#' as the first non-whitespace char on the line.
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*/
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bool line_is_comment(const char *s)
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{
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int i = first_non_white_space(s);
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return (i >= 0 && s[i] == '#');
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}
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/**
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* @brief Extract node names from a line from the map file.
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*
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* @param buf - Input buffer.
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* @param n1 - Output buffer for the first node name. Must be at least MAXNODENAME+1 long.
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* @param n2 - Ditto for the second node name.
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* @return int - Returns the number of correctly parsed node names. If the return value is 2, both n1
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* and n2 contain node names. If the return value is less than 2, parsing of at least one node name
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* failed, in which case the content of n1 and n2 are undefined.
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*/
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int parse_map_line(const char *buf, char *n1, char *n2)
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{
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// Create a format string the will do the work.
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char fmt[20];
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// This will generate the format string " %40s %40s" if MAXNODENAME is 40.
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snprintf(fmt, sizeof(fmt), " %%%ds %%%ds", MAXNODENAME, MAXNODENAME);
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// sscanf does all the necessary parsing.
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// Node names must be separated by whitespace.
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// Whitespace before the first node name is allowed.
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// Anything after the second node name is ignored.
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int n = sscanf(buf, fmt, n1, n2);
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// The return value from sscanf contains the number of properly parsed format codes, i.e. the
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// number of node names.
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return n;
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}
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/**
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* FUNCTION TO TRAVERSE THE GRAPH
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* @g: pointer to the graph
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* @src: pointer to source node
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* @dest: pointer to destination node
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*/
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bool find_path(graph *g, node *src, node *dest)
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{
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// Mark the starting node as seen
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g = graph_node_set_seen(g, src, true);
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dlist *neighbours = dlist_empty(NULL);
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// Put it in an empty queue
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queue *q = queue_enqueue(queue_empty(NULL), src);
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while (!queue_is_empty(q))
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{
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// pick the first node from queue
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src = queue_front(q);
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q = queue_dequeue(q);
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// if node equals destinatiom node, return true
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if (nodes_are_equal(src, dest))
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{
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// Deallocate the queue and list
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queue_kill(q);
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dlist_kill(neighbours);
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return true;
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}
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// remove list before making new.
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if (neighbours != NULL)
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{
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dlist_kill(neighbours);
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}
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// get the neighbours
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neighbours = graph_neighbours(g, src);
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dlist_pos p = dlist_first(neighbours);
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// Iterate over the lists of neigbours
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while (!dlist_is_end(neighbours, p))
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{
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if (!graph_node_is_seen(g, dlist_inspect(neighbours, p)))
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{
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// Mark unseen node as seen and put in queue
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g = graph_node_set_seen(g, dlist_inspect(neighbours, p), true);
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q = queue_enqueue(q, dlist_inspect(neighbours, p));
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}
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p = dlist_next(neighbours, p);
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}
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}
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// Deallocate the list and the queue
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dlist_kill(neighbours);
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queue_kill(q);
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return false;
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}
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/**
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* check_node_name - function used to find errors in node name
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*
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* Returns: Exit faliure if error in map file
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*/
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void check_node_name(char *n1, char *n2, char *data)
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{
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int k = parse_map_line(data, n1, n2);
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//Print error if number of correct node names is not 2
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if (k != 2)
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{
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fprintf(stderr, "Error reading the file\n");
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exit(EXIT_FAILURE);
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}
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//Check for non alphanumeric characters
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for (int j = 0; j < strlen(n1); j++)
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{
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if (isalnum(n1[j])==0)
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{
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fprintf(stderr, "Error non alphanumeric\n");
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exit(EXIT_FAILURE);
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}
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}
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for (int i = 0; i < strlen(n2); i++)
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{
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if (isalnum(n2[i])==0)
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{
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fprintf(stderr, "Error non alphanumeric\n");
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exit(EXIT_FAILURE);
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}
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}
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}
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/**
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* insert_nodes - insert the nodes to the graph
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* Returns: A graph with the input nodes inserted
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*/
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graph *insert_nodes(graph *g, char *n1, char *n2)
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{
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g = graph_insert_node(g, n1);
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g = graph_insert_node(g, n2);
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// Get pointers to the nodes from the graph
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node *m1 = graph_find_node(g, n1);
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node *m2 = graph_find_node(g, n2);
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// Check that both nodes exist
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if (m1 == NULL || m2 == NULL)
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{
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fprintf(stderr, "Error: node not found for edge: %s - %s\n", n1, n2);
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exit(EXIT_FAILURE);
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}
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// Insert the edges between the source and destination nodes and between the nodes themselves
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g = graph_insert_edge(g, m1, m1);
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g = graph_insert_edge(g, m2, m2);
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g = graph_insert_edge(g, m1, m2);
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return g;
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}
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/**
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* graph_from_file - reads the file and constructs a graph with it's contents
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* Returns: A pointer to the constructed graph
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*/
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graph *graph_from_file(int argc, char *argv[])
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{
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char data[40];
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// Open the file
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if (argc != 2)
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{
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fprintf(stderr, "Usage: %s <filename>\n", argv[0]);
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return NULL;
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}
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const char *filename = argv[1];
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// Print error message if file did not read correctly an exit program
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FILE *fptr = fopen(filename, "r");
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if (fptr == NULL)
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{
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perror("Error opening file\n");
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return NULL;
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}
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// Read the first line of the map-file
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fgets(data, 40, fptr);
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// Ignore comments and blank rows
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while (line_is_blank(data) || line_is_comment(data))
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{
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fgets(data, 40, fptr);
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}
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//Check that first non blank or coment line is a digit
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for (int i = 0; i < strlen(data) - 1; i++)
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{
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if (!isdigit(data[i]))
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{
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fprintf(stderr, "Error: first row is not a number\n");
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exit(EXIT_FAILURE);
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}
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}
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// Read the number of edges in the map-file and create an empty graph
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int nr_of_edges = atoi(data);
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graph *g = graph_empty(2 * nr_of_edges);
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// Iterates over the edge imputs
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for (int i = 0; i < nr_of_edges; i++)
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{
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// Read the data, parse the data and insert it into nodes in the graph
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fgets(data, 40, fptr);
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char n1[MAXNODENAME + 1];
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char n2[MAXNODENAME + 1];
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check_node_name(n1,n2,data);
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g = insert_nodes(g,n1,n2);
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}
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// Close the file and return the graph
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fclose(fptr);
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return g;
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}
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/**
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* main - The main program that handles user inputs and runs all of the help functions
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*
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* Returns: 0 if program exits normally
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*
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*/
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int main(int argc, char *argv[])
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{
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// Read the file and insert it into a graph
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graph *g = graph_from_file(argc, argv);
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// If file opening fails
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if (g == NULL)
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{
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return EXIT_FAILURE;
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}
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char src[MAXNODENAME + 1];
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char dest[MAXNODENAME + 1];
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char fmt[20];
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char buf[100];
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// Print the user interface
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printf("Enter origin and destination (quit to exit): ");
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// This will generate the format string " %40s %40s" if MAXNODENAME is 40.
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snprintf(fmt, sizeof(fmt), " %%%ds %%%ds", MAXNODENAME, MAXNODENAME);
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while (fgets(buf, sizeof(buf), stdin) != NULL)
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{
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// Reads the input from the user
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sscanf(buf, fmt, src, dest);
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// Quit the program if the user enters "quit"
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if (strcmp(src, "quit") == 0)
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{
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break;
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}
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// Check that the nodes exist in the graph
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node *nsrc = graph_find_node(g, src);
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node *ndest = graph_find_node(g, dest);
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if (nsrc == NULL || ndest == NULL)
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{
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printf("One or both nodes not found in the graph.\n");
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}
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// If the nodes exist check if there is a path and print the result
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else if (find_path(g, nsrc, ndest))
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{
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printf("There is a path from %s to %s.\n\n", src, dest);
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g = graph_reset_seen(g);
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}
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else
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{
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printf("There is no path from %s to %s.\n\n", src, dest);
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g = graph_reset_seen(g);
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}
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printf("Enter origin and destination (quit to exit): ");
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}
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// Print exit message and kill the graph
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printf("Normal exit.\n");
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graph_kill(g);
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return 0;
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}
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