[Link] https://www.acmicpc.net/problem/2252
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import java.util.*;
import java.io.*;
public class Main {
static BufferedReader br;
public static void main(String[] args) throws IOException {
br = new BufferedReader(new InputStreamReader(System.in));
StringBuilder sb = new StringBuilder();
int[] arr = getArr();
int n = arr[0], m = arr[1];
ArrayList<HashSet<Integer>> al = new ArrayList<>();
for(int i = 0; i < n; i++) al.add(new HashSet<Integer>());
int[] deg = new int[n];
boolean[] visit = new boolean[n];
for(int i = 0; i < m; i++) {
arr = getArr();
int a = arr[0] - 1, b = arr[1] - 1;
deg[b]++;
al.get(a).add(b);
}
Queue<Integer> q = new LinkedList<Integer>();
for(int i = 0; i < n; i++) {
if(!visit[i] && deg[i] != 0) continue;
q.add(i);
while(!q.isEmpty()) {
int cur = q.poll();
if(visit[cur]) continue;
visit[cur] = true;
sb.append(cur + 1).append(" ");
for(int v : al.get(cur)) {
if(--deg[v] == 0) q.offer(v);
}
}
}
print(sb);
}
static int toi(String s) { return Integer.parseInt(s); }
static String[] getLine() throws IOException { return br.readLine().split(" "); }
static int[] getArr() throws IOException { return Arrays.stream(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray(); }
static <T> void print(T s) { System.out.print(s); }
static <T> void println(T s) { System.out.println(s); }
}