import java.io.*; import java.util.ArrayDeque; import java.util.ArrayList; import java.util.StringTokenizer; public class Main { public static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out), 1024 * 64); public static int N, M; public static ArrayList> list; public static int[] degree; public static ArrayDeque deque; public static void main(String[] args) throws Exception { FastReader fr = new FastReader(); N = fr.nextInt(); M = fr.nextInt(); list = new ArrayList<>(); degree = new int[N]; for(int i = 0; i < N; i++) { list.add(new ArrayList<>()); } for(int i = 0; i < M; i++) { int from = fr.nextInt() - 1; int to = fr.nextInt() - 1; list.get(from).add(to); degree[to]++; } deque = new ArrayDeque<>(); for(int i = 0; i < N; i++) { if(degree[i] == 0) { deque.add(i); // 정점이 0이면 시작점 } } while(!deque.isEmpty()) { int current = deque.removeFirst(); bw.write((current + 1) + " "); for(int i = 0; i < list.get(current).size(); i++) { int k = list.get(current).get(i); degree[k]--; if(degree[k] == 0) { deque.add(k); } } } bw.flush(); bw.close(); } public static class FastReader { private final DataInputStream din; private final int BUFFER_SIZE = 1 << 16; private final byte[] buffer; private int bufferPointer, bytesRead; public FastReader() { din = new DataInputStream(System.in); buffer = new byte[BUFFER_SIZE]; bufferPointer = bytesRead = 0; } public String readLine() throws IOException { byte[] buf = new byte[BUFFER_SIZE]; // input line length int cnt = 0, c; while ((c = read()) != -1) { if (c == '\n') { break; } buf[cnt++] = (byte) c; } return new String(buf, 0, cnt); } public int nextInt() throws IOException { int ret = 0; byte c = read(); while (c <= ' ') { c = read(); } boolean neg = (c == '-'); if (neg) { c = read(); } do { ret = ret * 10 + c - '0'; } while ((c = read()) >= '0' && c <= '9'); if (neg) { return -ret; } return ret; } public long nextLong() throws IOException { long ret = 0; byte c = read(); while (c <= ' ') c = read(); boolean neg = (c == '-'); if (neg) c = read(); do { ret = ret * 10 + c - '0'; } while ((c = read()) >= '0' && c <= '9'); if (neg) return -ret; return ret; } public double nextDouble() throws IOException { double ret = 0, div = 1; byte c = read(); while (c <= ' ') c = read(); boolean neg = (c == '-'); if (neg) c = read(); do { ret = ret * 10 + c - '0'; } while ((c = read()) >= '0' && c <= '9'); if (c == '.') { while ((c = read()) >= '0' && c <= '9') { ret += (c - '0') / (div *= 10); } } if (neg) return -ret; return ret; } private void fillBuffer() throws IOException { bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE); if (bytesRead == -1) { buffer[0] = -1; } } private byte read() throws IOException { if (bufferPointer == bytesRead) { fillBuffer(); } return buffer[bufferPointer++]; } } }

코드 #487