Common Elements.java

// { Driver Code Starts
//Initial Template for Java

/*package whatever //do not write package name here */

import java.io.*;
import java.util.*;
class GFG {
	public static void main (String[] args) {
	    
	    //taking input using Scanner class
		Scanner sc = new Scanner(System.in);
		
		//taking total count of testcases
		int t=sc.nextInt();
		while(t-->0)
		{
		    //taking total count-1 of elements 
		    int n=sc.nextInt();
		    
		    //Declaring and Initializing an ArrayList-1
		    ArrayList<Integer>v1=new ArrayList<>();
		    
		    //adding elements to the ArrayList-1
		    for(int i=0;i<n;i++)
		    {
		        v1.add(sc.nextInt());
		    }
		    
		    //taking total count-2 of elements 
		    int m=sc.nextInt();
		    
		    //Declaring and Initializing an ArrayList-2
		    ArrayList<Integer>v2=new ArrayList<>();
		    
		    //adding elements to the ArrayList-2
		    for(int i=0;i<m;i++)
		    {
		        v2.add(sc.nextInt());
		    }
		    
		    //calling the method common_element
		    //and passing ArrayList 1, 2 as arguments
		    //and storing the results in a new ArrayList
		    ArrayList<Integer>ans=common_element(v1, v2);
		    
		    //printing the elements of the new ArrayList
		    for(int i:ans)
		    System.out.print(i+" ");
		    
		    System.out.println();
		}
	}
	

 // } Driver Code Ends


//User function Template for Java

public static ArrayList<Integer> common_element(ArrayList<Integer>v1, ArrayList<Integer>v2)
{
    Collections.sort(v1);
    Collections.sort(v2);
    
    int i = 0;
    int j = 0;
    int n = v1.size();
    int m = v2.size();
    ArrayList<Integer> ans = new ArrayList<Integer>();
    
    while (i < n && j < m) {
        if (v1.get(i) == v2.get(j)) {
            ans.add(v1.get(i));
            i++;
            j++;
        }
        else if (v1.get(i) > v2.get(j)) {
            j++;
        }
        else if (v1.get(i) < v2.get(j))
            i++;
    }
    
    return ans;
}


// { Driver Code Starts.

}  // } Driver Code Ends