# Segregate even and odd numbers | Set 3

Given an array of integers, segregate even and odd numbers in the array. All the even numbers should be present first, and then the odd numbers.

Examples:

```Input : 1 9 5 3 2 6 7 11
Output : 2 6 5 3 1 9 7 11

Input : 1 3 2 4 7 6 9 10
Output : 2 4 6 10 7 1 9 3
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

We have discussed two different approaches in below posts:

The idea discussed in this post is based on Lomuto’s Partition Scheme

1. Maintain a pointer to the position before first odd element in the array.
2. Traverse the array and if even number is encountered then swap it with the first odd element.
3. Continue the traversal.

## C++

 `// CPP code to segregate even odd ` `// numbers in an array ` `#include ` `using` `namespace` `std; ` ` `  `// Function to segregate even odd numbers ` `void` `arrayEvenAndOdd(``int` `arr[], ``int` `n) ` `{ ` ` `  `    ``int` `i = -1, j = 0; ` `    ``int` `t; ` `    ``while` `(j != n) { ` `        ``if` `(arr[j] % 2 == 0) { ` `            ``i++; ` ` `  `            ``// Swapping even and odd numbers ` `            ``swap(arr[i], arr[j]); ` `        ``} ` `        ``j++; ` `    ``} ` ` `  `    ``// Printing segregated array ` `    ``for` `(``int` `i = 0; i < n; i++) ` `        ``cout << arr[i] << ``" "``; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `arr[] = { 1, 3, 2, 4, 7, 6, 9, 10 }; ` `    ``int` `n = ``sizeof``(arr) / ``sizeof``(``int``); ` `    ``arrayEvenAndOdd(arr, n); ` `    ``return` `0; ` `} `

## Java

 `// java code to segregate even odd ` `// numbers in an array ` `public` `class` `GFG { ` `      `  `    ``// Function to segregate even ` `    ``// odd numbers ` `    ``static` `void` `arrayEvenAndOdd( ` `                  ``int` `arr[], ``int` `n) ` `    ``{ ` `      `  `        ``int` `i = -``1``, j = ``0``; ` `        ``while` `(j != n) { ` `            ``if` `(arr[j] % ``2` `== ``0``) ` `            ``{ ` `                ``i++; ` `      `  `                ``// Swapping even and ` `                ``// odd numbers ` `                ``int` `temp = arr[i]; ` `                ``arr[i] = arr[j]; ` `                ``arr[j] = temp; ` `            ``} ` `            ``j++; ` `        ``} ` `      `  `        ``// Printing segregated array ` `        ``for` `(``int` `k = ``0``; k < n; k++) ` `             ``System.out.print(arr[k] + ``" "``); ` `    ``} ` `    `  `    ``// Driver code ` `    ``public` `static` `void` `main(String args[]) ` `    ``{ ` `        ``int` `arr[] = { ``1``, ``3``, ``2``, ``4``, ``7``,  ` `                            ``6``, ``9``, ``10` `}; ` `        ``int` `n = arr.length; ` `        ``arrayEvenAndOdd(arr, n); ` `    ``} ` `} ` ` `  `// This code is contributed by Sam007 `

## Python3

 `# Python3 code to segregate even odd  ` `# numbers in an array  ` ` `  `# Function to segregate even odd numbers  ` `def` `arrayEvenAndOdd(arr,n): ` `    ``i ``=` `-``1` `    ``j``=` `0` `    ``while` `(j!``=``n): ` `        ``if` `(arr[j] ``%` `2` `=``=``0``): ` `            ``i ``=` `i``+``1` ` `  `            ``# Swapping even and odd numbers  ` `            ``arr[i],arr[j] ``=` `arr[j],arr[i] ` `             `  `        ``j ``=` `j``+``1` `     `  `    ``# Printing segregated array  ` `    ``for` `i ``in` `arr: ` `        ``print` `(``str``(i) ``+` `" "` `,end``=``'') ` `         `  `# Driver Code ` `if` `__name__``=``=``'__main__'``: ` `    ``arr ``=` `[ ``1` `,``3``, ``2``, ``4``, ``7``, ``6``, ``9``, ``10``] ` `    ``n ``=` `len``(arr) ` `    ``arrayEvenAndOdd(arr,n) ` ` `  `# This code was contributed by  ` `# Yatin Gupta `

## C#

 `// C# code to segregate even odd ` `// numbers in an array ` `using` `System; ` ` `  `class` `GFG { ` `     `  `    ``// Function to segregate even ` `    ``// odd numbers ` `    ``static` `void` `arrayEvenAndOdd( ` `                  ``int` `[]arr, ``int` `n) ` `    ``{ ` `     `  `        ``int` `i = -1, j = 0; ` `        ``while` `(j != n) { ` `            ``if` `(arr[j] % 2 == 0) ` `            ``{ ` `                ``i++; ` `     `  `                ``// Swapping even and ` `                ``// odd numbers ` `                ``int` `temp = arr[i]; ` `                ``arr[i] = arr[j]; ` `                ``arr[j] = temp; ` `            ``} ` `            ``j++; ` `        ``} ` `     `  `        ``// Printing segregated array ` `        ``for` `(``int` `k = 0; k < n; k++) ` `            ``Console.Write(arr[k] + ``" "``); ` `    ``} ` ` `  `    ``// Driver code     ` `    ``static` `void` `Main() ` `    ``{ ` `        ``int` `[]arr = { 1, 3, 2, 4, 7,  ` `                            ``6, 9, 10 }; ` `        ``int` `n = arr.Length; ` `        ``arrayEvenAndOdd(arr, n); ` `    ``} ` `} ` ` `  `// This code is contributed by Sam007 `

## PHP

 ` `

Output:

```2 4 6 10 7 1 9 3
```

Time Complexity : O(n)
Auxiliary Space : O(1)