Identify and count duplicates in array ?

[garnachito]

Hi guys I been trying this for almost 5 hours and I'm starting to get frustrated...

So, this is the problem, I have an array:

MR = new int[4][4];

Stored in the array I have 16 numbers from 1 to 20 but some of them maybe repeated, I need to identify which numbers are repeated and how many times.

Let´s say, "Number 3 has been found 4 times"... "Number 1 has been found 2 times"... "Number 9 has been found 0 times"

Here's the full code:

import java.awt.event.*;
import javax.swing.*;

public class arraysum extends JFrame implements ActionListener{
	
	int i,ii;
	int[][] M,M1,MR;
	String arregloR="", arreglo1="", arreglo2="";
	
	public arraysum(){
		
		setLayout(null);
		
		M = new int[4][4];
		M1 = new int[4][4];
		MR = new int[4][4];
		
		for(i=0;i<=3;i++){
			
			for(ii=0;ii<=3;ii++){
				
				M[i][ii]=1 + (int) (Math.random() * 9);
				M1[i][ii]=1 + (int) (Math.random() * 9);
				MR[i][ii]=M[i][ii] + M1[i][ii];
				
			}
			
		}
		
		
	}
		
	
	public static void main(String[]args){
	
		arraysum ventana=new arraysum();
		ventana.setBounds(100,50,600,600);
		ventana.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		ventana.setVisible(true);
		ventana.setResizable(false);
		
	}
}

Thanks in advance

[AndrewM16921]

What I would do, since you know the limitations of the values that can be held in the array, is construct a 1-dimensional array of size 20 (i.e. from 1 to 20, but may want to make it size 21 to avoid confusing indices and numbers). Each value will be initialized to 0. Then, go through every number in your 2-dimensional array and every time you encounter a number, increment the value in that index of the 1-dimensional array. At the end, go through that 1-dimensional array and print out any value over 1.

So, something like...

...

int[] counts = new int[21];

for(int i = 0; i < 4; i++)
{
	for(int j = 0; j < 4; j++)
	{
		counts[ MR[i][j] ]++;
	}
}

for(int i = 1; i < counts.length; i++)
{
	if(counts[i] > 1)
	{
		System.out.println("Number " + i + " found " + counts[i] + " times.");
	}
}

...

[garnachito]

Thanks a lot for your answer dude (I didn't see it before)

But I finally figured out how to do it... I'll post the code as soon as I finish the whole idea.

Thanks again for answer I appreciate it.