Java: Segregate all 0s on left side and all 1s on right side of a given array of 0s and 1s

Last update on May 09 2025 12:48:24 (UTC/GMT +8 hours)

42. Separate 0s and 1s in an array of 0s and 1s

Write a Java program to separate 0s and 1s in an array of 0s and 1s into left and right sides.

Pictorial Presentation:

Sample Solution:

Java Code:

// Import necessary Java libraries.
import java.util.*;
import java.lang.*;

// Define a class named Main.
public class Main
{
    // The main method for executing the program.
    public static void main(String[] args) 
    {  
        // Define an array of integers containing 0s and 1s.
        int nums[] = {0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 1};
        int i, nums_size = nums.length;
        int left = 0, right = nums_size - 1;
        
        // Print the original array.
        System.out.println("Original Array : " + Arrays.toString(nums));  

        // Perform segregation of 0s and 1s in the array.
        while (left < right) 
        {
            /* While 0 at the left, increment the left index. */
            while (nums[left] == 0 && left < right)
                left++;

            /* While we see 1 at the right, decrement the right index. */
            while (nums[right] == 1 && left < right)
                right--;

            if (left < right) 
            {
                // Swap 0 and 1 and increment left and decrement right.
                nums[left] = 0;
                nums[right] = 1;
                left++;
                right--;
            }
        }

        // Print the array after segregation.
        System.out.println("Array after segregation is : " + Arrays.toString(nums));  
    }
}

Sample Output:

                                                                              
Original Array : [0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 1]
Array after segregation is : [0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1]

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to move all negative numbers to one side of an array.
• Write a Java program to sort an array consisting only of 0s, 1s, and 2s without using the sort function.
• Write a Java program to find the minimum number of swaps required to group all 1s together in a binary array.
• Write a Java program to count the number of subarrays where the number of 0s and 1s is equal.

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