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  1. import java.util.*;
  2.  
  3. class Graph {
  4.     public static void main(String[] args) {
  5.         int n, m;
  6.         Scanner scanner = new Scanner(System.in);
  7.         n = scanner.nextInt();
  8.         m = scanner.nextInt();
  9.  
  10.         ArrayList<Integer> gr[] = new ArrayList[n];
  11.         for (int i = 0; i < n; i++) {
  12.             gr[i] = new ArrayList<>();
  13.         }
  14.  
  15.         int s = 0;
  16.         for (int i = 0; i < m; i++) {
  17.             int u, v;
  18.             u = scanner.nextInt();
  19.             v = scanner.nextInt();
  20.             gr[u - 1].add(v - 1);
  21.             gr[v - 1].add(u - 1);
  22.         }
  23.  
  24.         LinkedList<Integer> queue = new LinkedList<>();
  25.         queue.push(s);
  26.         boolean used[] = new boolean[n];
  27.         used[s] = true;
  28.  
  29.         while (!queue.isEmpty()) {
  30.             int v = queue.peek();
  31.             queue.pop();
  32.             for (int i = 0; i < gr[v].size(); ++i) {
  33.                 int to = gr[v].get(i);
  34.                 if (!used[to]) {
  35.                     used[to] = true;
  36.                     queue.push(to);
  37.                 }
  38.             }
  39.         }
  40.         String answer = "YES";
  41.         for (int i = 0; i < used.length; i++) {
  42.             if (used[i] == false) {
  43.                 answer = "NO";
  44.             }
  45.         }
  46.         System.out.println(answer);
  47.     }
  48. }
  49.  
Success #stdin #stdout 0.06s 321344KB
comments (?)
stdin
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4 5
1 2
2 1
2 4
2 4
4 2
stdout
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NO
https://ideone.com/dG0kxm
graph connectivity
language:
Java (HotSpot 12)
created:
7 years ago
visibility:
public

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