[Java] 백준 2623번 음악프로그램 - 위상 정렬

https://www.acmicpc.net/problem/2623

2623번: 음악프로그램

 

import java.util.*;
import java.io.*;

public class g2_2623 {
    static FastScanner fs = new FastScanner();
    static PrintWriter pw = new PrintWriter(System.out);
    static int n, m;
    static List<Node> list = new ArrayList<>();
    static Queue<Integer> q = new LinkedList<>(), ans = new LinkedList<>();

    public static void main(String[] args) {
        n = fs.nextInt();
        m = fs.nextInt();
        for (int i=0;i<=n;i++) list.add(new Node());

        for (int i=0;i<m;i++){
            int s = fs.nextInt();
            int[] temp = fs.readArray(s);
            for (int j=0;j<s-1;j++){
                list.get(temp[j]).next.add(temp[j + 1]);
                list.get(temp[j + 1]).degree++;
            }
        }

        for (int i=1;i<=n;i++){
            if (list.get(i).degree == 0) q.add(i);
        }
        solve();

        if (ans.size() == n) for (Integer i : ans) pw.println(i);
        else pw.println(0);

        pw.close();
    }

    static void solve(){
        while (!q.isEmpty()){
            int now = q.poll();
            ans.add(now);
            for (Integer i : list.get(now).next){
                if (--list.get(i).degree == 0) q.add(i);
            }
        }
    }

    static class Node {
        int degree;
        List<Integer> next = new LinkedList<>();

        public Node(){}
    }

    // ----------input function----------

    static void sort(int[] a) {
        ArrayList<Integer> L = new ArrayList<>();
        for (int i : a)
            L.add(i);
        Collections.sort(L);
        for (int i = 0; i < a.length; i++)
            a[i] = L.get(i);
    }

    static class FastScanner {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer("");

        String next() {
            while (!st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        int[] readArray(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt();
            return a;
        }

        long nextLong() {
            return Long.parseLong(next());
        }
    }
}