Segregate 0s and 1 using 2 pointer Java

 Given an array arr consisting of only 0's and 1's in random order. Modify the array in-place to segregate 0s onto the left side and 1s onto the right side of the array.


Examples :


Input: arr[] = [0, 0, 1, 1, 0]

Output: [0, 0, 0, 1, 1]

Explanation:  After segregation, all the 0's are on the left and 1's are on the right. Modified array will be [0, 0, 0, 1, 1].

Input: arr[] = [1, 1, 1, 1]

Output: [1, 1, 1, 1]

Explanation: There are no 0s in the given array, so the modified array is [1, 1, 1, 1]

Expected Time Complexity: O(n)

Expected Auxiliary Space: O(1)




//{ Driver Code Starts



// Initial Template for Java


import java.io.*;

import java.util.*;


public class Main {


    public static void main(String[] args) throws Exception {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        int t;

        t = Integer.parseInt(br.readLine());

        while (t-- > 0) {

            String line = br.readLine();

            String[] tokens = line.split(" ");


            // Create an ArrayList to store the integers

            ArrayList<Integer> array = new ArrayList<>();


            // Parse the tokens into integers and add to the array

            for (String token : tokens) {

                array.add(Integer.parseInt(token));

            }


            int[] arr = new int[array.size()];

            int idx = 0;

            for (int i : array) arr[idx++] = i;


            new Solution().segregate0and1(arr);

            for (int i = 0; i < array.size(); i++) {

                System.out.print(arr[i] + " ");

            }

            System.out.println();

            // System.out.println("~");

        

System.out.println("~");

}

    }

}


// } Driver Code Ends



// User function Template for Java


class Solution {

    

    public static void swap(int a,int b)

    {

        int temp=a;

        a=b;

        b=temp;

    }

    

    void segregate0and1(int[] arr) {

        // code here

        

        

        int start=0;

        int end=arr.length-1;

        

        while(start <end)

        {

            

            if(arr[start]==0)

            {

                start++;

                else

                {

                    if(arr[end]==0)

                    {

                        swap(arr[start],arr[end]);

                        start++;

                        end--;

                    }

                    

                }

            }

            else

            {

                end--;

            }

        }

    }

}


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