#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define NMAX 50005
struct Node {
int data;
struct Node *next;
};
typedef struct {
struct Node *head;
struct Node *tail;
int size;
} LinkedList;
typedef struct {
LinkedList **neighbors;
int nodes;
} ListGraph;
void init_list(LinkedList *list) {
list->head = NULL;
list->tail = NULL;
list->size = 0;
}
void init_list_graph(ListGraph *graph, int nodes) {
graph->nodes = nodes;
graph->neighbors = malloc(nodes * sizeof(LinkedList));
if (graph->neighbors == NULL) {
perror("Not enough memory to initialize the adjacency list!");
exit(-1);
}
for (int i = 0; i < nodes; ++i) {
graph->neighbors[i] = malloc(sizeof(LinkedList));
if (graph->neighbors[i] == NULL) {
perror("Not enough memory to initialize the adjacency list!");
exit(-1);
}
init_list(graph->neighbors[i]);
}
}
void add_nth_node(LinkedList *list, int n, int new_data) {
struct Node *prev, *curr;
struct Node *new_node;
if (list == NULL) {
return;
}
if (n > list->size) {
n = list->size;
} else if (n < 0) {
return;
}
curr = list->head;
prev = NULL;
while (n > 0) {
prev = curr;
curr = curr->next;
--n;
}
new_node = malloc(sizeof(struct Node));
if (new_node == NULL) {
perror("Not enough memory to add element!");
exit(-1);
}
new_node->data = new_data;
new_node->next = curr;
if (prev == NULL) {
list->head = new_node;
} else {
prev->next = new_node;
}
if (new_node->next == NULL) {
list->tail = new_node;
}
list->size++;
}
void add_edge_list_graph(ListGraph *graph, int src, int dest) {
struct Node *p;
for (p = graph->neighbors[src]->head; p; p = p->next) {
if (p->data == dest) {
return;
}
}
add_nth_node(graph->neighbors[src], (1 <<30), dest);
}
void dfs_topo_sort(ListGraph *lg, int node, int *visited, int *stack, int *n) {
// printf("%d\n", node);
struct Node *p;
visited[node] = 1;
for (p = lg->neighbors[node]->head; p; p = p->next) {
if (visited[p->data] == 0) {
dfs_topo_sort(lg, p->data, visited, stack, n);
}
}
stack[*n] = node;
// printf("added to stack on %d: %d\n", *n, node);
*n = *n + 1;
}
void topo_sort(ListGraph *lg, FILE *out) {
int i, viz[NMAX], n = 0, stack[NMAX];
memset(viz, 0, NMAX);
for (i = 1; i < lg->nodes; ++i) {
if (viz[i] == 0) {
dfs_topo_sort(lg, i, viz, stack, &n);
}
}
for (i = n - 1; i >= 0; i--) {
fprintf(out, "%d ", stack[i]);
}
}
void print_int_linkedlist(LinkedList *list) {
struct Node *curr;
if (list == NULL) {
return;
}
curr = list->head;
while (curr != NULL) {
printf("%d ", curr->data);
curr = curr->next;
}
printf("\n");
}
void print_list_graph(ListGraph *g) {
int i;
for (i = 1; i <= g->nodes; i++) {
printf("%d: ", i);
print_int_linkedlist(g->neighbors[i]);
}
}
int main() {
FILE *in = fopen("sortaret.in", "rt"), *out = fopen("sortaret.out", "wt");
int n, m, i, x, y;
ListGraph *lg = malloc(sizeof(ListGraph));
fscanf(in, "%d %d", &n, &m);
init_list_graph(lg, n + 1);
for (i = 0; i < m; ++i) {
fscanf(in, "%d %d", &x, &y);
add_edge_list_graph(lg, x, y);
}
//print_list_graph(lg);
topo_sort(lg, out);
fprintf(out, "\n");
fclose(in);
fclose(out);
}