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#include "cycle_detection.h"
#include "graph.h"
#include "linked_list.h"
#include "vector.h"
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
void cycle_detection(Graph *g) {
int n = g->num_vertices;
int *indegree = calloc(n, sizeof(int));
if (!indegree) {
fprintf(stderr, "Memory allocation failed: could not create list.\n");
free(indegree);
return;
}
LinkedList *queue = linked_list_new();
if (!queue) {
fprintf(stderr, "Memory allocation failed: could not create queue.\n");
free(indegree);
return;
}
Vector *list = vector_new();
if (!list) {
fprintf(stderr, "Memory allocation failed: could not create vector.\n");
free(indegree);
linked_list_delete(queue);
return;
}
// Compute in-degrees
for (int i = 0; i < n; i++) {
for (int j = 0; j < (int)g->vertices[i].out_neighbours->size; j++) {
Vertex neighbor = *(Vertex *)
g->vertices[i].out_neighbours->data[j];
indegree[neighbor.id]++;
}
}
// Add all vertices with no incoming edges
for (int i = 0; i < n; i++) {
if (indegree[i] == 0)
linked_list_append(queue, (void *)(intptr_t)i);
}
// Process queue for topological sort
while (queue->size != 0) {
int top = (int)(intptr_t)linked_list_popfront(queue);
vector_push(list, (void *)(intptr_t)top);
// Process all neighbors of current vertex
for (int j = 0; j < (int)g->vertices[top].out_neighbours->size; j++) {
Vertex neighbor = *(Vertex *)
g->vertices[top].out_neighbours->data[j];
indegree[neighbor.id]--;
if (!indegree[neighbor.id])
linked_list_append(queue, (void *)(intptr_t)neighbor.id);
}
}
// Output result
if ((int)list->size != n)
fprintf(stdout, "CYCLE DETECTED!\n");
else {
for (int i = 0; i < (int)list->size; i++) {
if (i != 0)
fprintf(stdout, ", ");
fprintf(stdout, "%d", (int)(intptr_t)vector_get(list, i));
}
fprintf(stdout, "\n");
}
linked_list_delete(queue);
vector_delete(list);
free(indegree);
}
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