BOJ11724.java

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

public class BOJ11724 {
    static boolean[][] map;
    static boolean[] visited;
    static int n;
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());

        n = Integer.parseInt(st.nextToken());
        int m = Integer.parseInt(st.nextToken());

        map = new boolean[n + 1][n + 1];
        visited = new boolean[n + 1];

        for (int i = 0; i < m; i++) {
            st = new StringTokenizer(br.readLine());
            int x = Integer.parseInt(st.nextToken());
            int y = Integer.parseInt(st.nextToken());

            map[x][y] = true;
            map[y][x] = true;
        }

        int answer = 0;
        for (int i = 1; i <= n; i++) {
            if (!visited[i]) {
                dfs(i);
                answer++;
            }
        }

        System.out.println(answer);
    }

    private static void dfs(int x) {
        visited[x] = true;
        for (int i = 1; i <= n; i++) {
            if (map[x][i] && !visited[i]) {
                dfs(i);
            }
        }
    }
}