Java Programs 17: Java Program to Find Duplicate Elements in Each Row of 2D Array

Hello Programers,

Problem:

How to find duplicate values in each row of 2D array. For example , we have 2d array as below:

4	67	34	90
9	4	11	100
6	12	9	4
78	87	4	2

Output should be : 4 , Because 4 is common in each row.

Solution:

This was really brainstorming as I want to avoid multiple for loops to solve this problem. My logic to solve above problem is as below:

1. I assume all elements in first row are duplicate elements i.e. exists in all rows.
2. I store all elements of first row in a HashSet say firstRow. I used HashSet just to add only unique elements as a row can have duplicate elements as well.
3. Now I take all elements of second row and store them in a different HashSet say secondRow.
4. Now I take intersection of firstRow and secondRow. It will return me only elements which are common in both rows.
5. If size of firstRow is zero, we will stop further iteration as it means there is no element which is common in all rows.
6. If size of firstRow is not zero, repeat step 4 for next row i.e. 3rd row.

Understand logic in Pic:

 

 

Java Programs:

package Arrays;

import java.util.HashSet;
import java.util.Set;

public class DuplicateElementInRows {

public static void main(String[] args) {

// An input array
int arrayValues[][] = { { 4, 67, 34, 90 }, { 9, 4, 11, 100 }, { 6, 12, 9, 4 }, { 78, 87, 4, 2 } };

// A set to store expected duplicates
Set expectedDuplicates = new HashSet();

// To store next row elements
Set deleteRow = new HashSet();

boolean duplicates=true;

// Iteration starts from here
for (int i = 0; i