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Java Program to remove duplicate element in an Array

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robaa
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2022-11-12
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We can remove duplicate element in an array by 2 ways: using temporary array or using separate index. To remove the duplicate element from array, the array must be in sorted order. If array is not sorted, you can sort it by calling Arrays.sort(arr) method.

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robaa
2022-11-12
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1) Remove Duplicate Element in Array using Temporary Array

public class RemoveDuplicateInArrayExample{  
public static int removeDuplicateElements(int arr[], int n){  
        if (n==0 || n==1){  
            return n;  
        }  
        int[] temp = new int[n];  
        int j = 0;  
        for (int i=0; i<n-1; i++){  
            if (arr[i] != arr[i+1]){  
                temp[j++] = arr[i];  
            }  
         }  
        temp[j++] = arr[n-1];     
        // Changing original array  
        for (int i=0; i<j; i++){  
            arr[i] = temp[i];  
        }  
        return j;  
    }  
       
    public static void main (String[] args) {  
        int arr[] = {10,20,20,30,30,40,50,50};  
        int length = arr.length;  
        length = removeDuplicateElements(arr, length);  
        //printing array elements  
        for (int i=0; i<length; i++)  
           System.out.print(arr[i]+" ");  
    }  
}

Output:

10 20 30 40 50

 

2) Remove Duplicate Element in Array using separate index

public class RemoveDuplicateInArrayExample2{  
    public static int removeDuplicateElements(int arr[], int n){  
        if (n==0 || n==1){  
            return n;  
        }    
        int j = 0;//for next element  
        for (int i=0; i < n-1; i++){  
            if (arr[i] != arr[i+1]){  
                arr[j++] = arr[i];  
            }  
        }  
        arr[j++] = arr[n-1];  
        return j;  
    }  
       
    public static void main (String[] args) {  
        int arr[] = {10,20,20,30,30,40,50,50};  
        int length = arr.length;  
        length = removeDuplicateElements(arr, length);  
        //printing array elements  
        for (int i=0; i<length; i++)  
           System.out.print(arr[i]+" ");  
    }  
}

 

Output:

10 20 30 40 50

 

Remove Duplicate Elements in Unsorted Array

If you have unsorted array, you need to sort it first. To do so, use Arrays.sort(arr) method.

import java.util.Arrays;  
public class RemoveDuplicateInArrayExample3{  
public static int removeDuplicateElements(int arr[], int n){  
        if (n==0 || n==1){  
            return n;  
        }  
        int[] temp = new int[n];  
        int j = 0;  
        for (int i=0; i<n-1; i++){  
            if (arr[i] != arr[i+1]){  
                temp[j++] = arr[i];  
            }  
         }  
        temp[j++] = arr[n-1];     
        // Changing original array  
        for (int i=0; i<j; i++){  
            arr[i] = temp[i];  
        }  
        return j;  
    }  
       
    public static void main (String[] args) {  
        int arr[] = {10,70,30,90,20,20,30,40,70,50};//unsorted array  
        Arrays.sort(arr);//sorting array  
        int length = arr.length;  
        length = removeDuplicateElements(arr, length);  
        //printing array elements  
        for (int i=0; i<length; i++)  
           System.out.print(arr[i]+" ");  
    }  
}

Output:

10 20 30 40 50 70 90

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