Finding Arrays are Disjoint or Not in Java

Understanding Disjoint Arrays

Two arrays are said to be disjoint if they have no elements in common.

We will explore three different methods to check if two arrays are disjoint in Java.

Method 1: Using Nested Loops

This method iterates through both arrays and checks for common elements.

import java.util.*;

public class DisjointArrays {
    static boolean areDisjoint(int[] arr1, int[] arr2) {
        for (int i : arr1) {
            for (int j : arr2) {
                if (i == j) {
                    return false;
                }
            }
        }
        return true;
    }
    
    public static void main(String[] args) {
        int[] arr1 = {1, 2, 3, 4};
        int[] arr2 = {5, 6, 7, 8};
        
        if (areDisjoint(arr1, arr2)) {
            System.out.println("Arrays are disjoint");
        } else {
            System.out.println("Arrays are not disjoint");
        }
    }
}
            

Method 2: Using Hashing

This method uses a HashSet to check for common elements efficiently.

import java.util.*;

public class DisjointArrays {
    static boolean areDisjoint(int[] arr1, int[] arr2) {
        Set set = new HashSet<>();
        for (int num : arr1) {
            set.add(num);
        }
        for (int num : arr2) {
            if (set.contains(num)) {
                return false;
            }
        }
        return true;
    }
    
    public static void main(String[] args) {
        int[] arr1 = {1, 2, 3, 4};
        int[] arr2 = {5, 6, 7, 8};
        
        if (areDisjoint(arr1, arr2)) {
            System.out.println("Arrays are disjoint");
        } else {
            System.out.println("Arrays are not disjoint");
        }
    }
}
            

Method 3: Using Set Intersection

This method uses set operations to determine if two arrays are disjoint.

import java.util.*;
import java.util.stream.Collectors;

public class DisjointArrays {
    static boolean areDisjoint(int[] arr1, int[] arr2) {
        Set set1 = Arrays.stream(arr1).boxed().collect(Collectors.toSet());
        Set set2 = Arrays.stream(arr2).boxed().collect(Collectors.toSet());
        
        set1.retainAll(set2);
        return set1.isEmpty();
    }
    
    public static void main(String[] args) {
        int[] arr1 = {1, 2, 3, 4};
        int[] arr2 = {5, 6, 7, 8};
        
        if (areDisjoint(arr1, arr2)) {
            System.out.println("Arrays are disjoint");
        } else {
            System.out.println("Arrays are not disjoint");
        }
    }
}