1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
|
import java.util.ArrayList;
import java.util.Scanner;
import java.util.Arrays;
import java.util.stream.IntStream;
public class Toposort {
private static ArrayList<Integer> toposort(ArrayList<Integer>[] adj) {
boolean[] visited = new boolean[adj.length];
ArrayList<Integer> order = new ArrayList<Integer>();
int[] postV = new int[adj.length];
int[] clock = new int[1];
dfs(adj, visited, postV, clock);
// https://stackoverflow.com/questions/951848/java-array-sort-quick-way-to-get-a-sorted-list-of-indices-of-an-array/35701049
int[] temp = IntStream.range(0, postV.length).boxed().sorted((i, j) -> postV[i] - postV[j]).mapToInt(ele -> ele).toArray();
Arrays.sort(postV);
for (int i = adj.length - 1; i > -1; i--) {
order.add(temp[i]);
}
return order;
}
private static void dfs(ArrayList<Integer>[] adj, boolean[] visited, int[] postV, int[] clock) {
for (int v = 0; v < adj.length; v++) {
if (!visited[v])
explore(v, adj, visited, postV, clock);
}
}
private static void explore(int v, ArrayList<Integer>[] adj, boolean[] visited, int[] postV, int[] clock) {
visited[v] = true;
for (int w : adj[v]) {
if (!visited[w])
explore(w, adj, visited, postV, clock);
}
postVisit(v, clock, postV);
}
private static void postVisit(int v, int[] clock, int[] postV) {
postV[v] = clock[0];
clock[0] = clock[0] + 1;
}
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int n = scanner.nextInt();
int m = scanner.nextInt();
ArrayList<Integer>[] adj = (ArrayList<Integer>[]) new ArrayList[n];
for (int i = 0; i < n; i++) {
adj[i] = new ArrayList<Integer>();
}
for (int i = 0; i < m; i++) {
int x, y;
x = scanner.nextInt();
y = scanner.nextInt();
adj[x - 1].add(y - 1);
}
ArrayList<Integer> order = toposort(adj);
for (int x : order) {
System.out.print((x + 1) + " ");
}
}
}
|
