Given an array arr(] of size N. The task is to find the first repeating element in the array of integers, i.e., an element that occurs more than once and whose index of first occurrence is smallest. code example

Example: first duplicate in array

import java.util.*; 
  
class Main 
{ 
    // This function prints the first repeating element in arr[] 
    static void printFirstRepeating(int arr[]) 
    { 
        // Initialize index of first repeating element 
        int min = -1; 
  
        // Creates an empty hashset 
        HashSet<Integer> set = new HashSet<>(); 
  
        // Traverse the input array from right to left 
        for (int i=arr.length-1; i>=0; i--) 
        { 
            // If element is already in hash set, update min 
            if (set.contains(arr[i])) 
                min = i; 
  
            else   // Else add element to hash set 
                set.add(arr[i]); 
        } 
  
        // Print the result 
        if (min != -1) 
          System.out.println("The first repeating element is " + arr[min]); 
        else
          System.out.println("There are no repeating elements"); 
    } 
  
    // Driver method to test above method 
    public static void main (String[] args) throws java.lang.Exception 
    { 
        int arr[] = {10, 5, 3, 4, 3, 5, 6}; 
        printFirstRepeating(arr); 
    } 
}