Having trouble creating an adjacency list - c

Question

I am trying to represent a graph using an adjacency list, but I am currently struggling with it. For some reason the edges are getting assigned to the wrong vertexes and I can't figure out why. I step through the code and the first 3 vertex pairs are added just fine but for some reason on the 4th nothing works right and I end up creating multiple new edges and not even the values of them are correct. A sample input is below as well as the C code. Anyone know why this might be happening? Note that
void print_distance(vertex*, int);
int check_an_edge(edge*);
void free_head(vertex*);
have not been implemented but free_head is used to free the entire list
5
(2,3)
(1,4)
(1,3)
(3,4)
(4,5)
#include <stdio.h>
#include <stdlib.h>
#include "input_error.h"
#define VertexToSearch 1
typedef struct node {
int value;
struct node* nextedge;
} edge;
typedef struct node1 {
int vertexnumber;
int distance;
struct node* edge;
} vertex;
vertex* load_file(char*);
void create_vertex_list(vertex*, int);
void create_new_edge(int, int, vertex*);
void print_distance(vertex*, int);
int check_an_edge(edge*);
void free_head(vertex*);
enum error program_error;
int main(int argc, char** argv) {
vertex* array;
array = load_file(argv[1]);
free_head(array);
return 0;
}
vertex* load_file(char* filename) {
int count;
int vertex1;
int vertex2;
FILE* file = fopen(filename, "r");
if (file == NULL) {
printf("%s did not open", filename);
program_error = FILE_FAILED_TO_OPEN;
exit(program_error);
}
fscanf(file, "%d", &count);
vertex* head = malloc(sizeof(vertex)* count);
create_vertex_list(head, count);
for (int i = 0; i < count; i++) {
fscanf(file, "\n(%d,%d)", &vertex1, &vertex2);
create_new_edge(vertex1, vertex2, head);
}
fclose(file);
return head;
}
void create_vertex_list(vertex head[], int count) {
vertex *new_node;
for (int i = 0; i < count; i++) {
new_node = malloc(sizeof (vertex));
new_node->vertexnumber = i + 1;
new_node->edge = NULL;
new_node->distance = -1;
*(head +i)= *new_node;
}
}
void create_new_edge(int vertex1, int vertex2, vertex* head) {
edge* new = malloc(sizeof (edge));
edge* new1 = malloc(sizeof (edge));
new->value = vertex1;
new1->value = vertex2;
new->nextedge = NULL;
new->nextedge = NULL;
if ((head +vertex1 - 1)->edge == NULL) {
(head +vertex1 - 1)->edge = new1;
} else {
edge* temp = (head +vertex1 - 1)->edge;
while (temp != NULL) {
if (temp->nextedge == NULL) {
temp->nextedge = new1;
break;
} else {
temp = temp->nextedge;
}
}
}
if ((head +vertex2 - 1)->edge == NULL) {
(head +vertex2 - 1)->edge = new;
} else {
edge* temp = (head +vertex2 - 1)->edge ;
while (temp != NULL) {
if (temp->nextedge == NULL) {
temp->nextedge = new1;
break;
} else {
temp = temp->nextedge;
}
}
}
}

Answer 1

In your create_new_edge function in the second if-statement you try to add new1. I think it's a copy-paste bug and you should change it to new.
if ((head +vertex2 - 1)->edge == NULL) {
(head +vertex2 - 1)->edge = new;
} else {
edge* temp = (head +vertex2 - 1)->edge ;
while (temp != NULL) {
if (temp->nextedge == NULL) {
temp->nextedge = new1; // Change here new1 to new
break;
} else {
emp = temp->nextedge;
}
}
}