데일리썽

문제 제목 : 바이러스

난이도 : 하

문제 유형 : DFS, BFS

추천 풀이 시간 : 30분 (못하면 2배 60분)

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

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;

public class Main {
    public static int pcCnt;
    public static int connCnt;
    public static ArrayList<ArrayList<Integer>> adjList = new ArrayList<>();
    public static boolean[] visited = new boolean[101];
    public static int resulCnt;

    public static void addEdge(int n, int m) {
        adjList.get(n).add(m);
    }

    public static void bfs(int pc) {
        Queue<Integer> queue = new LinkedList<Integer>();
        queue.offer(pc);
        visited[pc] = true;

        while (!queue.isEmpty()) {
            int now = queue.poll();
            resulCnt++;
            for (int i = 0; i < adjList.get(now).size(); i++) {
                int adjNode = adjList.get(now).get(i);
                if (!visited[adjNode]) {
                    queue.offer(adjNode);
                    visited[adjNode] = true;

                }
            }
        }


    }

    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        pcCnt = sc.nextInt();
        connCnt = sc.nextInt();

        for (int i = 0; i < pcCnt + 1; i++) {
            adjList.add(new ArrayList<Integer>());
        }

        for (int i = 0; i < connCnt; i++) {
            int pc1 = sc.nextInt();
            int pc2 = sc.nextInt();
            addEdge(pc1, pc2);
            addEdge(pc2, pc1);
        }

        bfs(1);
        System.out.println(resulCnt - 1);
    }
}