Unique numbers in one array

Question

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Hello,I have problem with counting unique numbers in array.I have tried one code but it has problem.

What I have tried:

Here is my code:

Java

package dan1;
 
import java.util.Scanner;
 
public class Nizovi7 {
    public static void main(String [] args){
        Scanner scanner = new Scanner(System.in);
        int counter = 0;
        int n = scanner.nextInt();
        int [] niz = new int [n];
        for(int i = 0;i < n;i++){
        	niz[i] = scanner.nextInt();
        }
        for(int i = 0;i<n;i++){
        	for(int j =0;j<n;j++){
        		if(niz[i]==niz[j]){
        			continue;
        		}
        		else{
        			counter++;
        		}
        	}
        }
        System.out.println(counter);
    }
}

Where is problem?

Posted 25-Sep-17 21:13pm

Member 13430000

Updated 25-Jan-18 2:19am

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CPallini · Answer 1 · 2017-09-25T23:29:00

Use an the HashSet<Integer> class: it provides automatic uniqueness:

Java

import java.util.HashSet;

public class Uniq
{
  public static void main(String [] args)
  {
    int ar[] = {1, 12, 53, 12, 24, 36, 17, 89, 12};

    HashSet<Integer> hs = new HashSet<Integer>();
    for (int i : ar)
    {
      hs.add(new Integer(i));
    }
    System.out.println(hs.size());
  }
}

OriginalGriff · Answer 2 · 2017-09-25T21:36:00

Solution 2

A suggestion: if you sort the array, then identical numbers are next to each other, and a lot easier to count...

And Java has a built-in Arrays.Sort method: Arrays.sort() in Java with examples - GeeksforGeeks[^]

Posted 25-Sep-17 21:36pm

OriginalGriff

Comments

Graeme_Grant 26-Sep-17 3:37am

deja vu? ;)

OriginalGriff 26-Sep-17 5:56am

I didn't see your solution while I was typing mine: the cat brought in a mouse halfway through, and Herself refuses to deal with them...

[no name] 26-Sep-17 4:33am

Really Worthy Answer Griff Sir..

Graeme_Grant · Answer 3 · 2017-09-25T21:26:00

I'm not a Java programmer but if you sort the array first in ascending or descending order, then testing for and counting unique numbers is very easy.

Here is a C# solution:

C#

int[] numbers = new int[] { 1, 5, 2, 9, 4, 7, 1, 5, 1, 9 };
Array.Sort(numbers);

int uniqueCount = 0, current = 0;
bool isRepeat = false;
foreach (var number in numbers)
{
    if (number != current)
    {
        if (current != 0 && !isRepeat)
            uniqueCount++;
        current = number;
        isRepeat = false;
    }
    else
    {
        isRepeat = true;
    }
}

Unique numbers in one array

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