Java: Rearrange all the elements of an given array of integers so that all the odd numbers come before all the even numbers

Last update on May 12 2025 13:12:46 (UTC/GMT +8 hours)

Rearrange Odd and Even Numbers

Write a Java program to rearrange all the elements of an given array of integers so that all the odd numbers come before all the even numbers.

Pictorial Presentation:

Sample Solution:

Java Code:

import java.util.*;

public class Exercise94 {
    public static void main(String[] args) {
        // Define an array of integers
        int[] array_nums = {1, 7, 8, 5, 7, 13, 0, 2, 4, 9};
        
        // Initialize an index variable to track even numbers
        int i = 0;

        // Display the original array
        System.out.println("Original Array: " + Arrays.toString(array_nums));

        // Find the first odd number's index (i)
        while (i < array_nums.length && array_nums[i] % 2 == 0)
            i++;
        
        // Rearrange the array such that odd numbers come after even numbers
        for (int j = i + 1; j < array_nums.length; j++) {
            if (array_nums[j] % 2 != 0) {
                // Swap even and odd numbers
                int temp = array_nums[i];
                array_nums[i] = array_nums[j];
                array_nums[j] = temp;
                i++;
            }
        }

        // Display the modified array
        System.out.println("New Array: " + Arrays.toString(array_nums));
    }
}

Sample Output:

Original Array: [1, 7, 8, 5, 7, 13, 0, 2, 4, 9]                        
New Array: [7, 5, 7, 13, 9, 1, 0, 2, 4, 8]

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to rearrange an array such that all prime numbers come before non-prime numbers.
• Write a Java program to rearrange an array such that negative numbers appear before positive numbers while preserving relative order.
• Write a Java program to rearrange an array such that all even numbers appear at even indices and odd numbers at odd indices.
• Write a Java program to sort an array such that even numbers are in ascending order and odd numbers are in descending order.

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