Eliminateing duplicates in an array

Question

I have this professor that wants us to make a using the method header Public static int[] eliminateDuplicates(int[] arr) The program uses a randomly generated array to see if there are duplications but the user gives a limit on how many indexes's the random array has. Here is what I have but it's not working.

import java.util.Random;
import java.util.Scanner;
public class Dublicates
{
    public static void main(String[] args)
    {
        Scanner input = new Scanner(System.in);
        Random generator = new Random();

        System.out.println("Enter array length: ");
        int[] a = new int[input.nextInt()];

        for (int i = 0; i<a.length; i++)
        {
            a[i] = generator.nextInt(a.length*2);
        }
        int[] result = eliminateDuplicates(a);
        System.out.println("The new numbers are: " + result.length);
        System.out.println("The double numbers were:");
        for (int b : result)
        {
            System.out.println(b + " ");
        }
    }
    public static int[] eliminateDuplicates(int[] arr)
    {
        int[] temp = new int[arr.length];
        int size = 0;
        for (int i = 0; i < arr.length; i++) {
            if (linearSearch(temp, arr[i]) == -1) {
                temp[size] = arr[i];
                size++;
            }
            int[] result = new int[size];
            for (int i = 0; i < size; i++) {
                result[i] = temp[i];
            }
            {
                return result;

            }
        }
    }
    public static int linearSearch(int[] arr, int key)
    {
        for(int i = 0; i<arr.length; i++)
        {
            if (key == arr[i])
                return i;
        }
        return -1;
    }
}

"but it's not working" means exactly what? What happens and what did you expect to happen? — Henry
– Henry, Commented Nov 5, 2018 at 5:02

Hyun I Kim · Accepted Answer · 2018-11-05 05:05:48Z

1

As your statements making the final result is inside the for loop, the statements inside for will only run once and will not give the right answer.

So you have to change your code as follows.

public static int[] eliminateDuplicates(int[] arr)
{
    int[] temp = new int[arr.length];
    int size = 0;
    for (int i = 0; i < arr.length; i++) {
        if (linearSearch(temp, arr[i]) == -1) {
            temp[size] = arr[i];
            size++;
        }
    }
    int[] result = new int[size];
    for (int i = 0; i < size; i++) {
        result[i] = temp[i];
    }

    return result;
}

answered Nov 5, 2018 at 5:05

Hyun I Kim

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1 Comment

Shivam Arora Over a year ago

It will not work because generator.nextInt(a.length*2) can generate 0 and by default array temp is initialised with 0 in its each index. So linearSearch on this array will not work

Shivam Arora · Accepted Answer · 2018-11-05 06:47:00Z

The default values in the integer array is 0, The Random.nextInt() can generate 0 random value, When you run linear search then 0 will not be included in the final resultant array. I have modify Random.nextInt() so that it will not generate 0 random number:

import java.util.Random;
import java.util.Scanner;
public class HelloCodiva
{
    public static void main(String[] args)
    {
        Scanner input = new Scanner(System.in);
        Random generator = new Random();

        System.out.println("Enter array length: ");
        int[] a = new int[input.nextInt()];      

        for (int i = 0; i<a.length; i++){
            a[i] = generator.nextInt(a.length*2)+1;//So that 0 is not generated
        }

        int[] result = eliminateDuplicates(a);

        for (int originalValue: a){
            System.out.println(originalValue+ " ");
        }

        System.out.println("The new numbers are: " + result.length);
        System.out.println("The double numbers were:");

        for (int b : result){
            System.out.println(b + " ");
        }
}

    public static int[] eliminateDuplicates(int[] arr)
    {
        int[] temp = new int[arr.length];
        int size = 0;
        for (int i = 0; i < arr.length; i++) {
            if (linearSearch(temp, arr[i]) == -1) {
                temp[size] = arr[i];
                size++;
            }
        }

        int[] result = new int[size];       
        System.arraycopy(temp, 0, result, 0, size);
       return result;
    }

    public static int linearSearch(int[] arr, int key)
    {
        for(int i = 0; i<arr.length; i++)
        {
            if (key == arr[i])
                return i;
        }
        return -1;
    }
}

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