Java Program to Store Even & Odd Elements of an Array into Separate Arrays

Given an array with N numbers and separate those numbers into two arrays by odd numbers or even numbers. The complete operation required O(n) time complexity in the best case. For optimizing the memory uses, the first traverse through an array and calculate the total number of even and odd numbers in it. Create two arrays with size calculated after traversing and start storing them.

Below is the implementation of the above approach:

Java

// Java Program to Store Even & Odd
// Elements of an Array into Separate Arrays

public class Even_Odd {

    // Print array method
    public static void printArray(int[] array)
    {
        for (int i = 0; i < array.length; i++)
            System.out.print(array[i] + " ");
        System.out.println();
    }
    public static void main(String[] args)
    {
        int n = 8;
        // array with N size
        int array[] = { 23, 55, 54, 9, 76, 66, 2, 91 };

        int evenSize = 0;
        int oddSize = 0;
        for (int i = 0; i < n; i++) {
            if (array[i] % 2 == 0)
                evenSize++;
            else
                oddSize++;
        }
        // odd and even arrays with size
        int[] even = new int[evenSize];
        int[] odd = new int[oddSize];
        // odd and even array iterator
        int j = 0, k = 0;
        for (int i = 0; i < n; i++) {
            if (array[i] % 2 == 0)
                even[j++] = array[i];
            else
                odd[k++] = array[i];
        }
        // print array method
        System.out.print("Even Array contains: ");
        printArray(even);
        System.out.print("Odd Array contains: ");
        printArray(odd);
    }
}

Output:

Even Array contains: 54 76 66 2 
Odd Array contains: 23 55 9 91 

Time Complexity: O(n)

Space Complexity: O(n)