# Separate 0s and 1s in an array

### Problem :

Given an array of 0’s and 1’s in random order , you need to separate 0’s and 1’s in an array.
For example:

### Solution :

#### Solution 1:

• Count number of 0’s in the array. Lets say we get X 0’s
• Once we get the count, put X 0’s in the array and put (n-X) 1’s in the latter part of array.
Java code:
Time Complexity : O(N)

#### Solution 2:

Algorithm:

Lets say array is arr[]

• Initialise two index variable , left=0 and right=arr.length-1
• Increment left variable until you get 1’s.
• Decrement right variable until you get 0’s
• If left < right, swap arr[left] and arr[right]
• In the end, you will see that you have 0’s on left side and 1’s on right side.

Java code:

### Java code to separate odd and even numbers in an array :

when you run above program, you will get below output:

import_contacts

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1. Rahul Kumar says:

package com.learn.dec.array;

public class SeperateZeroOnes {

public static void main(String[] args) {
int arr[]={0,1,0,0,1,1,1,0,1};

System.out.println(“Original Array: “);
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i]+" ");
}

int l = 0 , r = arr.length – 1;

while (l arr[r]){

int temp = arr[l] ;
arr[l] = arr[r];
arr[r] = temp;
}
l++;
r–;

}
System.out.println(“\nSorted Array: “);
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i]+" ");
}

}

}

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