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  1. /**
  2.  * PROBLEM STATEMENT
  3.  * In a social network, a person can invite friends of his/her friend. 
  4.   John wants to invite and add new friends. Complete the program below so that it prints 
  5.   the names of the persons to whom John can send a friend request.
  6.  
  7.  * Input Format: The first line contains the value of the N which represent the number of friends.
  8.  				Next N lines contain the name of the friend F followed by the number of friends of F 
  9.   				and finally their names separated by space.
  10.   
  11.  * Boundary Conditions: 2 <= N <= 10
  12.  * Output Format: The names to which John can send a friend request.
  13.  
  14.  * Example Input/Output 1:
  15.  * Input:
  16. 	  3
  17. 	  Mani 3 Ram Raj Guna
  18. 	  Ram 2 Kumar Kishore
  19. 	  Mughil 3 Praveen Naveen Ramesh
  20.  
  21.  * Output:Raj Guna Kumar Kishore Praveen Naveen Ramesh
  22.  * 
  23.  * Explanation:Ram is not present in the output as Ram is already John's friend.
  24.  * 
  25.  * Example Input/Output 2:
  26.  * Input:
  27. 	 4
  28. 	 Arjun 3 Bhuvana Ramya Rajesh
  29. 	 Naveen 2 Arjun Sangeetha
  30. 	 Rajesh 3 Narmada Madan Suresh
  31. 	 Suresh 2 Pawan Adhil
  32.  * Output:Bhuvana Ramya Sangeetha Narmada Madan Pawan Adhil
  33. **/
  34. import java.util.HashSet;
  35. import java.util.Scanner;
  36. import java.util.StringTokenizer;
  37.  
  38. class Ideone {
  39.     public static void main(String[] args) {
  40.         Scanner sc = new Scanner(System.in);
  41.         int N = sc.nextInt();   // No of friends
  42.         sc.nextLine();
  43.         HashSet<String> hs = new HashSet<>();   // to store name of the John's friends 
  44.         String invitation = "";
  45.         for(int i =0; i < N; i++)
  46.         {
  47.             String str = sc.nextLine();
  48.             String friend = "";
  49.             int j =0;
  50.             while(str.charAt(j)!= ' ')  
  51.             {
  52.                 friend = friend + str.charAt(j++);
  53.                 hs.add(friend);     // add the name before the number to HashSet
  54.             }
  55.             j= j+2;
  56.             invitation=invitation+str.substring(j)+" "; // remove name of John's friend from the string and store back remaining string
  57.         }        
  58.         int j =0;
  59.         StringTokenizer st = new StringTokenizer(invitation); // divide string into tokens
  60.         while(st.hasMoreTokens())
  61.         {
  62.             String str = st.nextToken();
  63.             if(!hs.contains(str))   {
  64.                 /* check if token(string) is already in hashset ie if the person already friend with John or not 
  65.                 if he is not then print str 
  66.                 */
  67.                 System.out.print(str+" ");
  68.             }
  69.         }
  70.     }
  71. }
  72.  
Success #stdin #stdout 0.14s 321280KB
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stdin
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3
Mani 3 Ram Raj Guna
Ram 2 Kumar Kishore
Mughil 3 Praveen Naveen Ramesh
stdout
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Raj Guna Kumar Kishore Praveen Naveen Ramesh
https://ideone.com/nvBKBA
language:
Java (HotSpot 12)
created:
7 years ago
visibility:
public

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