BOJ_2623_음악프로그램_java

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

2623번: 음악프로그램

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;

/**
 백준 2623번 음악프로그램
 골드 3
 */
public class BOJ_2623_음악프로그램 {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        StringBuilder sb = new StringBuilder();

        int N = Integer.parseInt(st.nextToken());
        int M = Integer.parseInt(st.nextToken());

        int[] inDegree = new int[N+1];
        List<Integer>[] edges = new List[N+1];
        for (int i = 1; i<N+1; i++){
            edges[i] = new ArrayList<>();
        }

        // 간선 정보 입력
        for (int i = 0; i<M; i++){
            st = new StringTokenizer(br.readLine());
            int peopleNum = Integer.parseInt(st.nextToken());
            int from = Integer.parseInt(st.nextToken());
            for (int j = 1; j<peopleNum; j++){
                int to = Integer.parseInt(st.nextToken());
                edges[from].add(to);
                inDegree[to]++;
                from = to;
            }
        }

        // 위상정렬
        Queue<Integer> queue = new LinkedList();
        int nodeCnt = 0;
        for (int i = 1; i<=N; i++){
            if (inDegree[i] == 0){
                queue.offer(i);
                while (!queue.isEmpty()){
                    int node = queue.poll();
                    sb.append(node).append("\n");
                    nodeCnt++;
                    inDegree[node] = -1;
                    for (int next : edges[node]){
                        inDegree[next]--;
                        if (inDegree[next] == 0){
                            queue.offer(next);
                        }
                    }
                }
            }
        }
        if (nodeCnt == N){
            System.out.println(sb.toString());
        }else {
            System.out.println(0);
        }
    }
}