020-003-002

Set Operations: Managing Collections Without Duplicates

Medium

Problem Description

HashSet Set Operations

In this problem, you will create a program that converts two integer lists into HashSets, finds their intersection (common elements) using the retainAll() method, sorts the result in ascending order, and displays it to standard output.

Use HashSet's retainAll() method to find the intersection.

Finding Intersection

Set<Integer> set1 = new HashSet<>(list1);
Set<Integer> set2 = new HashSet<>(list2);
set1.retainAll(set2); // set1 becomes the intersection

Learning Points

  • retainAll() is a destructive operation that modifies the original set
  • Convert to List and use Collections.sort() for sorted output
  • Use addAll() for union, removeAll() for difference

Test Cases

※ Output examples follow programming industry standards

Normal case
Input:
4
1 2 3 4
4
3 4 5 6
Expected Output:
3 4
Boundary case
Input:
3
1 2 3
3
4 5 6
Expected Output:
No common elements

Your Solution

Current Mode:● My Code
import java.util.Scanner;

public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
// Write your code here

sc.close();
}
}
0 B / 5 MB

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