[BOJ] 2606. 바이러스

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

접근 방법

전형적인 BFS ,DFS 문제이다.

1번의 컴퓨터로 바이러스가 진행이 되므로

Queue 에 1을 넣어준 후 BFS를 돌려주면 되는 문제이다.

Need Know

1. BFS

전체 코드 ( Java )

import java.io.*;
import java.util.LinkedList;
import java.util.Queue;
import java.util.StringTokenizer;

class Main{
    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
    static int computer;
    static int count;
    static boolean[][] con;
    static boolean[] visit;
    public static void main(String[] args) throws IOException{
        set();
        solve();

        br.close();
        bw.flush();
        bw.close();
    }
    static void set() throws IOException {
        computer = Integer.parseInt(br.readLine());
        count = Integer.parseInt(br.readLine());

        con = new boolean[computer+1][computer+1];
        visit = new boolean[computer+1];
        for(int i=0; i<count; i++){
            StringTokenizer st = new StringTokenizer(br.readLine());
            int a = Integer.parseInt(st.nextToken());
            int b = Integer.parseInt(st.nextToken());

            con[a][b] = true;
            con[b][a] = true;
        }
    }
    static void solve() throws IOException {
        bfs();
        int result = 0;
        for(int i=2; i<computer+1; i++){
            if(visit[i]) {
                result++;
            }
        }
        bw.write(result+"");
    }
    static void bfs(){
        Queue<Integer> queue = new LinkedList<>();
        queue.add(1);
        visit[1] = true;
        while(!queue.isEmpty()){
            int peek = queue.poll();

            for(int i=0; i<computer+1; i++){
                if(con[peek][i] && !visit[i]){
                    queue.add(i);
                    visit[i] = true;
                }
            }
        }
    }
}