Remove duplicates from integer array

Question

I having a problem with coding this:

Write a static method named removeDuplicates that takes as input an array of integers and returns as a result a new

Answer 1

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

// Remove duplicates from a list of integers
public class IntegerUtils {
    public static void main(String[] args) {
        int intArray[] = {1, 2, 4, 2, 67, 4, 9};
        List<Integer> uniqueList = removeDuplicates(intArray);
        uniqueList.stream().forEach(p -> System.out.println(p));
    }

    public static List<Integer> removeDuplicates(int[] intArray) {
        return Arrays.stream(intArray).boxed().distinct().collect(Collectors.toList());
    }
}

Answer 2

public int[] removeRepetativeInteger(int[] list){
        if(list.length == 0){
            return null;
        }
        if(list.length == 1){
            return list;
        }

    ArrayList<Integer> numbers = new ArrayList<>();
    for(int i = 0; i< list.length; i++){
        if (!numbers.contains(list[i])){
            numbers.add(list[i]);
        }
    }
    Iterator<Integer> valueIterator = numbers.iterator();
    int[] resultArray = new int[numbers.size()]; 
    int i = 0;
    while (valueIterator.hasNext()) {
        resultArray[i] = valueIterator.next();
        i++;
    }
    return resultArray;     

}

Answer 3

Iterate over the array and populate a set because sets cannot contain duplicates. Then copy the elements from the set into a new array and return it. This is shown below:

public static int[] removeDuplicates(int[] array) {
    // add the ints into a set
    Set<Integer> set = new HashSet<Integer>();
    for (int i = 0; i < array.length; i++) {
        set.add(array[i]);
    }

    // copy the elements from the set into an array
    int[] result = new int[set.size()];
    int i = 0;
    for (Integer u : set) {
        result[i++] = u;
    }
    return result;
}

Answer 4

Try this

public static int[] removeDuplicates(int[] s) {     
    Integer[] array = new HashSet<Integer>(Arrays.asList(ArrayUtils.toObject(s))).toArray(new Integer[0]);      
    return ArrayUtils.toPrimitive(array);
}

Edit: Updated with Apache Lang to convert to primitives.

Answer 5

You can do naively though. First you need to sort the array. You can do it using any of sorting algorithms. I did use quick sort. And then check a position with its next position. If they are not same, add value in a new array, otherwise skip this iteration.

Sample Code (Quick Sort):

 public static void quickSort(int[] array, int low, int high) {
    int i = low;
    int j = high;

    int pivot = array[low + (high - low) / 2];

    while (i <= j) {
        while (array[i] < pivot) i++;
        while (array[j] > pivot) j--;
        if (i <= j) {
            exchange(array, i, j);
            i++;
            j--;
        }
    }
    if (0 < j) quickSort(array, 0, j);
    if (i < high) quickSort(array, i, high);
}

public static void exchange(int[] array, int i, int j) {
    int temp = array[i];
    array[i] = array[j];
    array[j] = temp;
}

Remove duplicates:

 public static int[] removeDuplicate(int[] arrays) {
    quickSort(arrays, 0, arrays.length - 1);

    int[] newArrays = new int[arrays.length];
    int count = 0;
    for (int i = 0; i < arrays.length - 1; i++) {
        if (arrays[i] != arrays[i + 1]) {
            newArrays[count] = arrays[i];
            count++;
        }
    }
    return newArrays;
}

Answer 6

Maybe you can use lambdaj (download here,website), this library is very powerfull for managing collections (..list,arrays), the following code is very simple and works perfectly:

import static ch.lambdaj.Lambda.selectDistinct;
import java.util.Arrays;
import java.util.List;

public class DistinctList {
     public static void main(String[] args) {
         List<Integer> numbers =  Arrays.asList(1,3,4,2,1,5,6,8,8,3,4,5,13);
         System.out.println("List with duplicates: " + numbers);
         System.out.println("List without duplicates: " + selectDistinct(numbers));
     }
}

This code shows:

List with duplicates: [1, 3, 4, 2, 1, 5, 6, 8, 8, 3, 4, 5, 13]
List without duplicates: [1, 2, 3, 4, 5, 6, 8, 13]

In one line you can get a distinct list, this is a simple example but with this library you can resolve more.

selectDistinct(numbers)

You must add lambdaj-2.4.jar to your project. I hope this will be useful.

Note: This will help you assuming you can have alternatives to your code.