Removing duplicate elements from Array in Core Java

Question

Without using collections,i have written a java program to remove duplicate integer element from an integer array,however the program is removing only one integer element and other integer element is left over.

Could you let me know how should i remove duplicate integer elements in the below core java program.In the below core java program i have to remove the duplicate integer element 5

Help provided will be appreciated.

Below is the Java code.

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class DeleteElementFromArray {

    static int[] a = {5,1,2,3,4,5,7,8,9,10};
    static int[] b = new int[10];
    static int i, k, f, j = 0;
    static int l = a.length;

    void DeletElementInt() {
         for (i = 0; i < l; i++) {
             if (i != k) {
                   if (i < k) {
                       b[i] = a[i];
                   } else{                    
                         b[i - 1] = a[i];
                   }  
             }
         }
     }       



    public static void main(String[] args) {
          DeleteElementFromArray d = new DeleteElementFromArray();
          System.out.println("Array Elements are ");
          for (i = 0; i < l; i++){
            System.out.println(a[i]); 
          }
          InputStreamReader is = new InputStreamReader(System.in);
          BufferedReader br = new BufferedReader(is);
          System.out.println("Enter the Element for Delete");
          try {
             String s = br.readLine();
             f = Integer.parseInt(s);
              for (i = 0; i < l; i++) {
                if (f == a[i]) {
                  System.out.println("Delete Element found from given array");
                  k = i;
                  j++;
                  d.DeletElementInt();
                }
              }
                 l = l - 1;
                 System.out.println("New Array ");
                 for (i = 0; i < l; i++) 
                 {
                      System.out.println(b[i]);
                 }
                 if (j == 0) {
                   System.out.println("Entered Element does not found from given array");
                 }
          } catch (IOException e) {
                System.out.println(e);
          }
    }
}


//output
/*
Array Elements are 
5
1
2
3
4
5
7
8
9
10
Enter the Element for Delete
5
Delete Element found from given array
New Array 
1
2
3
4
5
7
8
9
10
*/

Answer 1

Use:

package Array;

import java.util.Scanner;

public class DuplicateArrayElement {
    
    //operation
    void duplicate(int arr[],int size) {
        
        int count=0;
        for(int i=0;i<size-1;i++) {
            for(int j=i+1;j<size;j++) {
                if(arr[i]==arr[j]) {
                    arr[i]=0;
                    
                    count++;
                }
            }
        }
        
        for(int i =0; i<size;i++) {
            if(arr[i]!=0) {
                System.out.println(" "+arr[i]);
            }
            
        }
        System.out.println("Total duplicate number : "+count);
    }
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        DuplicateArrayElement duplicateArrayElement = new DuplicateArrayElement();
        try {
            System.out.println("Enter the size of array:");
            int size = input.nextInt();
            int arr[] = new int[size];
            System.out.println("Enter the elements: ");
            for (int i = 0; i < size; i++) {
                arr[i] = input.nextInt();
            }

            System.out.println("Orignal Array: ");
            for (int i : arr) {
                System.out.print(" " + i);
            }
            System.out.println("\nAfter removing duplicate values :");
            duplicateArrayElement.duplicate(arr, size);
        } catch (ArrayIndexOutOfBoundsException ex) {
            System.out.println(ex);
        } finally {
            input.close();
        }

    }
}

Answer 2

public static void main(String[] args) {
    int a[]={1,4,3,2,6,5,7,3,5,4,2};
    int b[]=new int[a.length];
    Arrays.sort(a);
    int j=0;
    for(int i=0;i<a.length;i++){
        while(i<a.length-1 && a[i]==a[i+1]){
            a[i]=999;  // This can be any tag which you are not going to have in your array
            i++;
        }
        if(a[i]!=999)
            b[j++]=a[i];
    }

    System.out.println(b);
}

Answer 3

Below is my solution:

First step:- Iterate through array with nested loops to find duplicates Second step:- If found duplicates copy all elements in new array except duplicate element.

Please find below code, any improvement would be appreciated.

public class DuplicateElements {

private static int[] arr = new int[]{3,2,4,4,5,3,8,2,4,9,10};

public static void main(String[] args) {
    for(int i=0;i<arr.length;i++){
        int arr_i = arr[i];
        for(int j=0;j<arr.length;j++){
            if(arr_i == arr[j] && i != j){
                removeElement(j);
            }
        }
    }

    for(int i=0;i<arr.length;i++){
        System.out.print(arr[i]+", ");
    }
}

public static void removeElement(int position){
    int[] intArr = new int[arr.length - 1];
    for(int i=0;i<position;i++){
        intArr[i] = arr[i];
    }
    for(int i=position+1;i<arr.length;i++){
        intArr[i-1] = arr[i];
    }
    arr = intArr;
}

}

Answer 4

import java.util.Scanner;

public class RemoveAllOccurences{

    static int[] removeAll(int[] a,int n){
        int[] dupl = new int[a.length];
        for(int i = 0;i < dupl.length;i++){
            dupl[i] = -999;
        }
        int index = 0;
        //looping over,finding all occurrences of n and creating new array that does not contain n.
        for(int i = 0;i < a.length;i++){
            if(a[i] != n){
                dupl[index++] = a[i];
            }
        }

        //returning array with all duplicates removed.
        return dupl;
    }

    public static void main(String[] args) {

        int[] a = {3,5,5,5,3,6,5,3,3};
        int numberToRemove;

        System.out.println("the array values are:");
        for(int i:a){
            System.out.print(a[i]+"\t");
        }

        Scanner sc = new Scanner(System.in);
        System.out.println("\nenter the number for which all occurences need to be deleted:");

        numberToRemove = sc.nextInt();

        int[] b = removeAll(a,numberToRemove);

        System.out.println("After removing all occurences of "+numberToRemove);
        for(int i:b){
            if(i != -999)
                System.out.print(i+"\t");
        }

    }
}

Answer 5

The first question when some one ask you to work with arrays should be. Do the order is important ?

Most problem with arrays can be solved by sorting it first and then the problem is reduced to trivial from complex as you always work on the same type of data. As Archimedes sad once "Give me a place to stand on, and I will move the Earth". The sort operation is that stand place.

When you sort your array, then you just need to traverse it and find that next item is equal to previous. This is trivial.

How ever if the order is important then we have a little bit harder task.

So first solution that pop i my mind is to create new point to stand. The rules are that array has items grater or equal then zero.

In this case we could do something like this.

1. We find the grates element in our source array.
2. We create a boolean array with size of grates item.
3. We move through each item of source list and
4. We check that boolean arrays position of value has false if so then we set it to true an print the result else we go to next item of source array.

The step 4 was simplified as we want to print the list. The technical aspect of returning new one with distinct values is trivial to.

So good luck.

Answer 6

is Arrays.sort() okay?

static int[] a = {5,1,2,3,4,5,7,8,9,10};
static int[] b = new int[a.length];

Arrays.sort(a);

b[0]=a[0];
int bIndex = 1;
for(int aIndex = 1; aIndex < a.length; aIndex++) {
    if(b[bIndex-1] != a[aIndex]) {
        b[bIndex] = a[aIndex];
        bIndex++;
    }
}

int[] result = Arrays.copyOfRange(b, 0, bIndex);

if this is for educational purposes another interesting approach could be to construct a tree structure with the numbers and flatten the tree to an array when all inserts are done.

Answer 7

First you have to sort your array. It will be much easier for you to remove the duplicates if you do. The Arrays class contains various methods (most of them are static) to manipulate arrays. Use Arrays.sort(array). If you're not allowed to, you have to use one of the many existing sorting algorithm. The simplest being Bubble sort.

Insert the first integer in your result array, and in a temporary variable which will contain the last inserted value. Parse the source array: if the current value is different than the temporary var, insert it in the result array (and update the temp var).

Be careful with the size of your return array.

Answer 8

Here is the fixed code:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class DelElem {

    static int[] a = {5,1,2,3,4,5,7,8,9,10};
    static int[] b = new int[10];
    static int f, i, k, j = 0;
    static int l = a.length;

    static void DeleteElementInt(int elementToDelete) {
        j = 0;
        for (int i = 0; i < l; i++)
            if (a[i] != elementToDelete)
                b[i - j] = a[i];
            else
                ++j;
    }



    public static void main(String[] args) {
        System.out.println("Array elements are:");
        for (i = 0; i < a.length; i++)
            System.out.println(a[i]);
        InputStreamReader is = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(is);
        System.out.print("Enter the element to be deleted: ");
        try {
            String s = br.readLine();
            f = Integer.parseInt(s);
            DeleteElementInt(f);
            System.out.println("New array:");
            for (i = 0; i < l - j; i++)
                System.out.println(b[i]);
            if (j == 0)
                System.out.println("Entered element was not found in the given array");
        } catch (IOException e) {
            System.out.println(e);
        }
    }
}


//output
/*
Array elements are:
5
1
2
3
4
5
7
8
9
10
Enter the element to be deleted: 5
New array:
1
2
3
4
7
8
9
10
*/