Smallest Positive missing number Java

PROGRAM TO FIND THE SMALLEST POSITIVE NUMBER MISSING FROM AN UNSORTED ARRAY

import java.util.*;

  

class MAIN

{

  

// Function to find the smallest

// positive missing number

static int findMissingPositive(int arr[], int n)

{

    // Default smallest Positive Integer

    int m = 1;

  

    // Store values in set which are

    // greater than variable m

    HashSet<Integer> x = new HashSet<Integer>();

  

    for (int i = 0; i < n; i++)

    {

        // Store value when m is less than

        // current index of given array

        if (m < arr[i])

        {

            x.add(arr[i]);

        }

        else if (m == arr[i])

        {

            // Increment m when it is equal

            // to current element

            m = m + 1;

  

            while (x.contains(m)) 

            {

                x.remove(m);

  

                // Increment m when it is one of the

                // element of the set

                m = m + 1;

            }

        }

    }

  

    // Return the required answer

    return m;

}

  

// Driver code

public static void main(String[] args) 

{

    int arr[] = { 2, 3, -7, 6, 8, 1, -10, 15 };

  

    int n = arr.length;

  

    // Function call

    System.out.println(findMissingPositive(arr, n));

}

}

OUTPUT

4

CREDITS:  https://www.geeksforgeeks.org/find-the-smallest-positive-number-missing-from-an-unsorted-array-set-3/