Java: Separate 0s on left side and 1s on right side of an array of 0s and 1s in random order

Last update on May 09 2025 12:51:31 (UTC/GMT +8 hours)

51. Separate 0s on left and 1s on right in array

Write a Java program that separates 0s on the left hand side and 1s on the right hand side from a random array of 0s and 1.

Pictorial Presentation:

Sample Solution:

Java Code:

// Import the necessary Java utility class for working with arrays.
import java.util.Arrays;

// Define the Main class.
public class Main {
    public static void main(String[] args)
    {
        // Create an array of integers containing 0s and 1s.
        int arr[] = new int[]{ 0, 0, 1, 1, 0, 1, 1, 1, 0 };
        int result[];
        
        // Print the original array.
        System.out.println("Original Array ");
        System.out.println(Arrays.toString(arr));

        // Get the length of the array.
        int n = arr.length;
 
        // Call the separate_0_1 method to separate 0s and 1s.
        result = separate_0_1(arr, n);
        
        // Print the rearranged array.
        System.out.println("New Array ");
        System.out.println(Arrays.toString(result));
    }
    
    // A method to separate 0s and 1s in an array.
    static int[] separate_0_1(int arr[], int n)
     {
        // Initialize a count to track the number of 0s.
        int count = 0;   
     
        // Count the number of 0s in the array.
        for (int i = 0; i < n; i++) {
            if (arr[i] == 0)
                count++;
        }
 
        // Set the first 'count' elements to 0.
        for (int i = 0; i < count; i++)
            arr[i] = 0;
 
        // Set the remaining elements to 1.
        for (int i = count; i < n; i++)
            arr[i] = 1;
    
        // Return the modified array.
        return arr;
     }       
}

Sample Output:

                                                                              
Original Array 
[0, 0, 1, 1, 0, 1, 1, 1, 0]
New Array 
[0, 0, 0, 0, 1, 1, 1, 1, 1]

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to count the number of 0s and 1s in a given binary array.
• Write a Java program to find the longest contiguous subarray with an equal number of 0s and 1s.
• Write a Java program to find the index of the first occurrence of 0 in a sorted binary array.
• Write a Java program to determine whether a binary array can be split into two parts with equal numbers of 0s and 1s.

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