[BOJ] 2606 바이러스

 

 

[문제]

https://www.acmicpc.net/problem/2606

 

 

 

[소스 코드]

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

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st;
		int n = Integer.parseInt(br.readLine());
		int m = Integer.parseInt(br.readLine());
		boolean[][] edge = new boolean[n+1][n+1];
		for(int i=0;i<m;i++) {
			st = new StringTokenizer(br.readLine());
			int a = Integer.parseInt(st.nextToken());
			int b = Integer.parseInt(st.nextToken());
			edge[a][b] = edge[b][a] = true;
		}
		boolean[] visit = new boolean[n+1];
		Queue<Integer> q = new LinkedList<>();
		q.offer(1);
		visit[1] = true;
		int cnt = 0;
		while(!q.isEmpty()) {
			int curr = q.poll();
			for(int v=2;v<=n;v++) {
				if(edge[curr][v] && !visit[v]) {
					cnt++;
					q.offer(v);
					visit[v] = true;
				}
			}
		}
		System.out.println(cnt);
	}
}