연결 요소의 개수(11724)

연결 요수의 개수 (11724)

풀이

• 방문하지 않은 노드들을 bfs 돌려 연결된 그룹의 수를 세주면 된다.

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.LinkedList;
import java.util.Queue;
import java.util.StringTokenizer;

class FastScanner {
    BufferedReader br;
    StringTokenizer st;

    public FastScanner() {
        br = new BufferedReader(new InputStreamReader(System.in));
    }

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

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

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

public class Main {
    static int arr[][];
    static boolean visited[];


    public static void main(String args[]) throws IOException {
        FastScanner sc = new FastScanner();

        int n = sc.nextInt();   // 정점
        int m = sc.nextInt();   // 간선
        int cnt = 0;

        arr = new int[n+1][n+1];
        visited = new boolean[n+1];

        for(int i=0; i<m; i++){
            int a = sc.nextInt();
            int b = sc.nextInt();

            arr[a][b] = 1;
            arr[b][a] = 1;
        }

       for(int i=1; i<=n; i++){
           if(!visited[i]) {
               bfs(i, n);
               cnt++;
           }
       }
        System.out.println(cnt);


    }

    public static void bfs(int start, int n) {
        Queue<Integer> queue = new LinkedList<>();
        queue.add(start);

        while(!queue.isEmpty()){
            int cur = queue.poll();

            for(int i=1; i<=n; i++){
                    if(arr[cur][i] == 1 && !visited[i]){
                        visited[i] = true;
                        queue.add(i);
                    }
            }
        }

    }



}