Logic seems OK but can't get final requirement to verify

Question about the task

How many potential friends does a person have?

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Hi all, So for this one, I think I've got the logic for getFriends correct. It passes the example, and make senses with other values for the index parameter. However, I can't this to verify requirement 4. I may be misinterpretting the meaning of the deep parameter. Help please. Thanks, Phil

Today we'll analyze some functionality of social networks. How do social networks know who to suggest as friends you might know? This task is easily solved using graphs.

Your task is to implement the Set<Integer> getAllFriendsAndPotentialFriends(int index, int deep) method, which returns the indices of people you are already friends with and of people you might know. After that, the removeFriendsFromSet method will run and produce the set of all potential friends of the person with the passed index, given a search depth specified by the deep parameter.
For simplicity, we will view everyone's relationships as a two-dimensional array called humanRelationships (see an example array in the generateRelationships method). Along the main diagonal, all elements are true because everybody knows himself or herself. The intersection of rows and columns indicates whether people have friended each other (if true, then the people have friended each other). If a person with index k has been friended by a person with index p, then that means that the person with index k is among the friends of the person with index p.

Two arguments are passed to the method:
int index - the index of a person in the array (starting from zero);
int deep - how deep to search for friends. If Mary is Natalie's friend and Julia is Mary's friend and the search depth = 1, then you need to add Mary to the set returned for Natalie. If the search depth = 2, then you need to add Mary, along with Julia as a potential friend, to the set returned for Natalie. If the search depth = 3, then you also need to add all of Julia's friends to the same set.
See the example in the main method.
The set returned by the getAllFriendsAndPotentialFriends method must not include index.

Requirements:

The Solution class must have a public Set<Integer> getAllFriendsAndPotentialFriends(int index, int deep) method.
The Solution class must have a boolean[][] humanRelationships class.
The set returned by the getAllFriendsAndPotentialFriends method must not include index.
The getAllFriendsAndPotentialFriends method must be implemented as outlined in the task conditions.

package com.codegym.task.task36.task3611; import java.util.*; /* How many potential friends does a person have? */ public class Solution { private boolean[][] humanRelationships; public static void main(String[] args) { Solution solution = new Solution(); solution.humanRelationships = generateRelationships(); Set<Integer> allFriendsAndPotentialFriends = solution.getAllFriendsAndPotentialFriends(4, 2); System.out.println(allFriendsAndPotentialFriends); // Expected: [0, 1, 2, 3, 5, 7] Set<Integer> potentialFriends = solution.removeFriendsFromSet(allFriendsAndPotentialFriends, 4); System.out.println(potentialFriends); // Expected: [2, 5, 7] } // Return test data private static boolean[][] generateRelationships() { return new boolean[][]{ {true}, //0 {true, true}, //1 {false, true, true}, //2 {false, false, false, true}, //3 {true, true, false, true, true}, //4 {true, false, true, false, false, true}, //5 {false, false, false, false, false, true, true}, //6 {false, false, false, true, false, false, false, true} //7 }; } public Set<Integer> getAllFriendsAndPotentialFriends(int index, int deep) { //write your code here boolean[][] relationships = generateRelationships(); Set<Integer> friends = new HashSet<>(); friends.add(index); Integer[] array; int depth = 0; while (depth++ < deep) { array = new Integer[friends.size()]; friends.toArray(array); for (int i : array) { friends.addAll(getFriends(relationships, i)); } } friends.remove(index); return friends; } public Set<Integer> getFriends(boolean[][] relationships, int index) { Set<Integer> friends = new HashSet<>(); for (int i = 0; i < relationships[index].length; i++) { if (relationships[index][i]) friends.add(i); } for (int i = index; i < relationships.length; i++) { if (index < relationships[i].length && relationships[i][index]) friends.add(i); } return friends; } // Remove from the set the people with whom you already have a relationship public Set<Integer> removeFriendsFromSet(Set<Integer> set, int index) { for (int i = 0; i < humanRelationships.length; i++) { if ((i < index) && (index < humanRelationships.length) && humanRelationships[index][i]) { set.remove(i); } else if ((i > index) && humanRelationships[i][index]) { set.remove(i); } } return set; } }

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Wei Cui

Level 39 , Newark, United States

21 April 2020, 19:53

public Set<Integer> getAllFriendsAndPotentialFriends(int index, int deep) {
       //write your code here
       Set<Integer> result = new HashSet<>();
       if (deep == 0) return result;
       for (int i = 0; i < humanRelationships.length; i++) {
           if (i < index) {
               if (humanRelationships[index][i]) {
                   result.add(i);
                   result.addAll(getAllFriendsAndPotentialFriends(i, deep - 1));
               }
           } else {
               if (humanRelationships[i][index]) {
                   result.add(i);
                   result.addAll(getAllFriendsAndPotentialFriends(i, deep - 1));
               }
           }
       }
       result.remove(index);
       return result;
   }

Guadalupe Gagnon

Level 37 , Tampa, United States

5 December 2019, 01:19

solution

One problem that I see is line 39, you shouldn't be calling generateRelationships() and using the values from that inside the method. You should be using the humanRelationships array on line 11.

Philip Butler

Level 32 , United Kingdom, United Kingdom

5 December 2019, 16:58

Thanks Guadalupe, That was it. I removed line 39 and instead of passing in the relationships, just referenced the class variable. I do find that CodeGymn fails tests when the code works as required. In this instance I can only image there is an assertion that getAllFriendsAndPotentialFriends has to reference this.humanRelationships. Thranks again for your help.

Guadalupe Gagnon

Level 37 , Tampa, United States

5 December 2019, 19:50

Trust me, i understand. There have been many tasks that had me pulling out my hair trying to figure out because my code worked but the validation system just didn't like it. You have to remember that the validation system is going to be testing the code you submit with test values. On top of that it is not flexible in the least and can be thrown off by simple things such as using static variables. For Example, a task to output 1-10 on the screen:

class Solution{
   static int count = 0;

   public static void main(String[] args){
      while(count != 10){
         System.out.println(++count);
   }
}

This code would fail verification, but if you moved count to inside the main method it passes?!?! Very frustrating. Remember this though: When they have you split up things into specific methods that is a good indication that they are going to pump in different values to test that the method works as specified.