백준 11724 연결 요소의 개수

import java.util.*;
public class Main {

	static int map [][];
	static boolean visited [];
	static int n;
	static int m; 
	
	static int count=0;
  
	
	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		n=sc.nextInt();//정점의 갯수
		m=sc.nextInt(); //간선의 갯수
		map=new int [n+1][n+1];
		visited=new boolean [n+1];
		Arrays.fill(visited, false);  
		for(int i=0; i<n+1;i++){
			Arrays.fill(map[i], 0);
		}
		for(int i=0;i<m;i++) {
			int a=sc.nextInt();	  
			int b=sc.nextInt();			
			map[a][b]=1;
            map[b][a]=1;
		}
		int ans=0;
		for(int i=0; i<n+1;i++){
			 if(!visited[i]) {
				 ans++;
				 dfs(i);
			 }
		}
		  
		 System.out.println(ans-1);	 	 
	}
	
	public static void dfs(int k) {
		visited[k]=true;
		for(int i=0;i<n+1;i++) {
			if(visited[i]==false&&map[k][i]==1) {
				count++;
				dfs(i);
				
			}
		}
	}
}