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Q2606.java
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Q2606.java
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package olympiad;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.StringTokenizer;
public class Q2606 {
private static int cnt;
private static int N;
private static int E;
private static ArrayList<Integer> edges[];
private static boolean visited[];
private static void dfs(int dest){
if(!visited[dest]){
visited[dest] = true;
cnt++;
for (int i = 0; i < edges[dest].size(); i++) {
dfs(edges[dest].get(i));
}
}
}
public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
StringTokenizer st;
N = Integer.parseInt(br.readLine());
E = Integer.parseInt(br.readLine());
visited = new boolean[N + 1];
edges = new ArrayList[N + 1];
for (int i = 1; i <= N; i++)
edges[i] = new ArrayList<Integer>();
for (int i = 0; i < E; i++) {
st = new StringTokenizer(br.readLine());
int u = Integer.parseInt(st.nextToken());
int v = Integer.parseInt(st.nextToken());
edges[u].add(v);
edges[v].add(u);
}
dfs(1);
bw.write((cnt - 1) + "\n");
br.close();
bw.close();
}
}