[백준]24444 알고리즘 수업 - 너비 우선 탐색 1

package baekjoon;

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

public class Main_2444 {
    static int N, M, cnt;
    static boolean[] visit;
    static int[] check;
    static ArrayList<ArrayList<Integer>> bfs = new ArrayList<>();
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine(), " ");
        N = Integer.parseInt(st.nextToken());       // 정점의 수
        M = Integer.parseInt(st.nextToken());       // 간선의 수
        int R = Integer.parseInt(st.nextToken());   // 시작정점

        for (int i = 0; i <= N; i++) {
            bfs.add(new ArrayList<>());
        }
        visit = new boolean[N+1];
        check = new int[N+1];
        for (int i = 0; i < M; i++) {
            StringTokenizer st2 = new StringTokenizer(br.readLine(), " ");
            int u = Integer.parseInt(st2.nextToken());
            int v = Integer.parseInt(st2.nextToken());

            bfs.get(u).add(v);
            bfs.get(v).add(u);
        }

        for (ArrayList<Integer> arrayList : bfs) {
            Collections.sort(arrayList);
        }

        bfs(R);

        for (int i = 1; i <= N; i++) {
            System.out.println(check[i]);
        }
    }

    public static void bfs(int start) {
        Queue<Integer> q = new LinkedList<>();
        visit[start] = true;
        check[start] = cnt++;
        q.add(start);
        while(!q.isEmpty()) {
            int u = q.poll();
            //System.out.println(">"+u);
            check[u] = cnt++;

            for (Integer integer : bfs.get(u)) {
                if(visit[integer]) {
                    continue;
                }
                q.add(integer);
                visit[integer] = true;
            }
        }
    }
}

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