How to remove Duplicate elements from a Sorted Array

This is another popular coding interview question. I had faced this question during my interview with Reliance Jio.

You are given a sorted array like { 2,2,2,2}, so the final array would be {2}.

Examples: 

Input:       arr[]={5,5,5,5}
Output:    arr[]={5}

Input:       arr[]={1, 2, 2, 3, 4, 4, 4, 5, 5}
Output:    arr[]={1,2,3,4,5}

Logic: To solve this problem, we will take another variable as j. Every time we will check i th element with i+1 th element. If it does not match, will increase j with j+1.

Program:

public class DuplicateArrayElement {
static int removeDuplicates(int arr[], int n)
    {
        if (n == 0 || n == 1)
            return n;
        
        //Taking extra index which will be increased based on iTh and i+1 Th index
        int j = 0;
      
        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;
    }

//** Main method to test the method removeDuplicates()**//

    public static void main (String[] args) 
    {
        int arr[] = {1, 2, 2, 3, 4, 4, 4, 5, 5};
        int n = arr.length;
         
        n = removeDuplicates(arr, n);
  
        for (int i=0; i<n; i++)
           System.out.print(arr[i]+" ");
    }
}