Error condition, how to implement it? - c

Question

So what my codes does at the moment is quite simple. It receives an input like this:
5 4
1 2
2 3
3 4
4 5
The first line of the input represents the number of Ids and the number of relations. The following line are those relations. The program sorts these pairs, for example: 1 comes before 2, 2 comes before 3 and so on. In this case the outup will be 1 2 3 4 5.
In case of contradictive input, such as:
4 4
1 2
2 3
3 2
3 4
It returns "Incoerente".
My current problem is my input is "non conclusive" such as:
4 4
1 2
3 1
3 4
4 2
In this case the program doesnt really know where to place the 4 (after or before the 1?). My program right now (with the input above) will print "3 1 2", and ignores the 4 for some reason. When this situation apears I want to print "OTHERERROR".
Here is my code:
#include <stdio.h>
#include <stdlib.h>
#define MAX 100
void create_graph();
void add(int vertex);
int del();
int isEmpty();
int find_indegree_of_vertex(int vertex);
int total_vertices;
int adjacent_matrix[MAX][MAX];
int queue[MAX];
int front = -1;
int rear = -1;
FILE *myFile;
int main(){
myFile = fopen("input.txt", "r");
int i;
int numberArray[2];
for(i=0;i<2;i++)
fscanf(myFile, "%1d", &numberArray[i]);
int N = numberArray[0];
int L = numberArray[1];
int vertex, count, topological_sort[MAX], indegree[MAX];
create_graph(N, L);
for(i = 0; i < total_vertices; i++){
indegree[i] = find_indegree_of_vertex(i);
if(indegree[i] == 0){
add(i);
}
}
count = 0;
while(!isEmpty() && count < total_vertices){
vertex = del();
topological_sort[++count] = vertex;
for(i = 0; i < total_vertices; i++){
if(adjacent_matrix[vertex][i] == 1){
if(adjacent_matrix[i][vertex] == 1){
printf("INCOERENTE !!!!!!!!!!!!!!!\n");
}
adjacent_matrix[vertex][i] = 0;
indegree[i] = indegree[i] - 1;
if(indegree[i] == 0){
add(i);
}
}
}
}
if(count < total_vertices){
printf("Incoerente\n");
exit(1);
}
printf("Topological Order of Vertices\n");
for(i = 1; i <= count; i++){
printf("%3d", topological_sort[i]+1);
}
printf("\n");
return 0;
}
void add(int vertex){
if(rear == MAX - 1){
printf("Queue Overflow\n");
}
else{
if (front == -1) {
front = 0;
}
rear = rear + 1;
queue[rear] = vertex ;
}
}
int isEmpty(){
if(front == -1 || front > rear ){
return 1;
}
else{
return 0;
}
}
int del(){
int element;
if (front == -1 || front > rear){
printf("Queue Underflow\n");
exit(1);
}
else{
element = queue[front];
front = front+1;
return element;
}
}
int find_indegree_of_vertex(int vertex){
int count, total_indegree = 0;
for(count = 0; count < total_vertices; count++){
if(adjacent_matrix[count][vertex] == 1){
total_indegree++;
}
}
return total_indegree;
}
void create_graph(int N, int L){
int count, maximum_edges, origin_vertex, destination_vertex;
total_vertices = N;
maximum_edges = L;
int integers[MAX];
int i =0;
int num;
while(fscanf(myFile, "%d", &num) > 0) {
integers[i] = num;
i++;
}
i=0;
printf("1a linha :%d %d\n", N, L);
for(count = 1; count <= maximum_edges; count++){
origin_vertex = integers[i]-1;
destination_vertex = integers[i+1]-1;
printf("pares a ser avaliados :%d %d\n", origin_vertex+1, destination_vertex+1);
if(origin_vertex > total_vertices || destination_vertex > total_vertices || origin_vertex < 0 || destination_vertex < 0){
printf("Edge Co-ordinates are Invalid\n");
count--;
}
else
adjacent_matrix[origin_vertex][destination_vertex] = 1;
if(count == maximum_edges){
break;
}
i+=2;
}
}