DFS

package Chat;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.StringTokenizer;

public class hii {
    static ArrayList<Integer>[] A;
    static boolean visited[];
    public static void main(String[] args) throws IOException {
        BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(bf.readLine());
        int n = Integer.parseInt(st.nextToken());//노드 개수
        int m = Integer.parseInt(st.nextToken());//간선 개수

        A = new ArrayList[n+1];
        visited = new boolean[n+1];

        //노드
        for (int i = 1; i <= n; i++) {
            A[i] = new ArrayList<>();
        }
        //간선
        for (int i = 0; i < m; i++){
            st = new StringTokenizer(bf.readLine());
            int startNode = Integer.parseInt(st.nextToken());
            int endNode = Integer.parseInt(st.nextToken());

            //양방향 엣지
            A[startNode].add(endNode);
            A[endNode].add(startNode);
        }

        int count = 0;
        for (int i = 1; i <= n; i++) {
            if(!visited[i]){
                //방문하지않은 노드가 없을때까지 반복
                count++;
                dfs(i);
            }
        }
        System.out.println(count);
    }
    static void dfs(int now){
        if(visited[now]) {return;}
        visited[now] = true;

        for (int i : A[now]) {
            if(!visited[i]){
                dfs(i);
            }
        }

    }
}