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  1. import java.util.Scanner;
  2. import java.util.ArrayList;
  3.  
  4. class Main
  5. {
  6. 	private static void dfs(int v, int p, ArrayList<ArrayList<Integer>> g , int[] A) {
  7. 		A[v]++;
  8. 		if (A[v]>1)
  9. 			return;
  10. 		for (int i=0; i<g.get(v).size(); i++)
  11. 		{
  12. 			if (g.get(v).get(i)!=p)
  13. 				dfs(g.get(v).get(i), v, g, A);
  14. 		}
  15. 	}
  16.  
  17. 	public static void main (String[] args)
  18. 	{
  19. 		Scanner scanner = new Scanner(System.in);
  20. 		int n = scanner.nextInt();
  21. 		int[] A = new int[n];
  22. 		ArrayList<ArrayList<Integer>> g = new ArrayList<ArrayList<Integer>>();
  23. 		for (int i=0; i<n; i++) {
  24. 			ArrayList<Integer> r = new ArrayList<Integer>();
  25. 			for (int j=0; j<n; j++) {
  26. 				int a = scanner.nextInt();
  27. 				if (a==1) {
  28. 					r.add(j);
  29. 				}
  30. 			}
  31. 			g.add(r);
  32. 		}
  33. 		int t=0;
  34. 		dfs(0, -1, g, A);
  35. 		for (int i=0; i<n; i++)
  36. 		{
  37. 			if (A[i]!=1)
  38. 			{
  39. 				t++;
  40. 				break;
  41. 			}
  42. 		}
  43. 		if (t!=0)
  44. 			System.out.print("NO");
  45. 		else
  46. 			System.out.print("YES");
  47. 	}
  48. }
Success #stdin #stdout 0.06s 2184192KB
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YES
https://ideone.com/jPKy0X
language:
Java (HotSpot 12)
created:
6 years ago
visibility:
public

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