# Length of the longest Subarray with only Even Elements

Given an array arr[]. The task is to find the length of the longest subarray of arr[] such that it contains only even elements.

Examples:

```Input : arr[] = { 5, 2, 4, 7 }
Output : Length = 2
subArr[] = {2, 4}

Input : arr[] = {9, 8, 5, 4, 4, 4, 2, 4, 1}
Output : Length 5
subArr[] = {4, 4, 4, 2, 4}
```

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

The idea is to observe that the largest subarray with only even elements is the maximum number of contiguous even elements in the array. Therefore, the task now reduces to find the maximum number of contiguous even elements in the array.

To do this, traverse the array using two variables, ans and current_count. The variable ans stores the final answer and current_count stores the length of subarray with only even numbers.

Now whenever an even element is found, keep incrementing the current_count and whenever an ODD element is found take the maximum of ans and current_count and reset current_count to zero.

At the end, ans will store the length of largest subarray with only even elements.

Below is the implementation of the above approach:

 `   `  `// C++ Program to find the Length of the ` `// largest Subarray with only even elements ` ` `  `#include ` `#include ` `using` `namespace` `std; ` ` `  `// Function to find the Length of the ` `// largest Subarray with only even elements ` `int` `maxEvenSubarray(``int` `array[], ``int` `N) ` `{ ` `    ``int` `ans = 0; ` `    ``int` `count = 0; ` ` `  `    ``// Iterate the loop ` `    ``for` `(``int` `i = 0; i < N; i++) { ` ` `  `        ``// Check whether the element is ` `        ``// even in continuous fashion ` `        ``if` `(array[i] % 2 == 0) { ` `            ``count++; ` `            ``ans = max(ans, count); ` `        ``} ` ` `  `        ``else` `{ ` `             `  `            ``// If element are not even in continuous ` `            ``// fashion, Reinitialize the count ` `            ``count = 0; ` `        ``} ` `    ``} ` ` `  `    ``// Check for the last element in the array ` `    ``ans = max(ans, count); ` `    ``return` `ans; ` `} ` ` `  `// Driver Code ` `int` `main() ` `{ ` `    ``int` `arr[] = { 9, 8, 5, 4, 4, 4, 2, 4, 1 }; ` ` `  `    ``int` `N = ``sizeof``(arr) / ``sizeof``(arr[0]); ` ` `  `    ``cout << maxEvenSubarray(arr, N); ` ` `  `    ``return` `0; ` `} `

 `// Java Program to find the Length of the longest ` `// Subarray with only Even Elements ` `public` `class` `GFG { ` ` `  `    ``// Function to find the Length of the longest ` `    ``// Subarray with only Even Elements ` `    ``static` `int` `maxEvenSubarray(``int` `array[], ``int` `N) ` `    ``{ ` `        ``int` `ans = ``0``; ` `        ``int` `count = ``0``; ` ` `  `        ``// Iterate the loop ` `        ``for` `(``int` `i = ``0``; i < array.length; i++) { ` ` `  `            ``// Check whether the element is ` `            ``// even in continuous fashion ` `            ``if` `(array[i] % ``2` `== ``0``) { ` `                ``count++; ` `                ``ans = Math.max(ans, count); ` `            ``} ` ` `  `            ``else` `{ ` `                ``// If element are not even in continuous ` `                ``// fashion. Reinitialize the count ` `                ``count = ``0``; ` `            ``} ` `        ``} ` ` `  `        ``// Check for the last element in the array ` `        ``ans = Math.max(ans, count); ` `        ``return` `ans; ` `    ``} ` ` `  `    ``// Driver Code ` `    ``public` `static` `void` `main(String args[]) ` `    ``{ ` `        ``int` `arr[] = { ``9``, ``8``, ``5``, ``4``, ``4``, ``4``, ``2``, ``4``, ``1` `}; ` ` `  `        ``int` `N = arr.length; ` ` `  `        ``System.out.println(maxEvenSubarray(arr, N)); ` `    ``} ` `} `

 `# Python3 Program to find the Length of the  ` `# largest Subarray with only even elements  ` ` `  `# Function to find the Length of the ` `# largest Subarray with only even elements ` `def` `maxEvenSubarray(array,N): ` `    ``ans ``=` `0` `    ``count ``=` `0` ` `  `    ``# Iterate the loop ` `    ``for` `i ``in` `range``(``0``,N): ` `         `  `        ``# Check whether the element is ` `        ``# even in continuous fashion ` `        ``if` `array[i]``%``2``=``=``0``: ` `            ``count ``+``=``1` `            ``ans ``=` `max``(ans,count) ` ` `  `        ``else``: ` ` `  `            ``# If element are not even in continuous ` `            ``# fashion, Reinitialize the count ` `            ``count ``=` `0` `             `  `    ``# Check for the last element in the array ` `    ``ans ``=` `max``(ans,count) ` `    ``return` `ans ` ` `  `# Driver code ` `if` `__name__``=``=``'__main__'``: ` `    ``arr ``=` `[``9``, ``8``, ``5``, ``4``, ``4``, ``4``, ``2``, ``4``, ``1``] ` `    ``N ``=` `len``(arr) ` `    ``print``(maxEvenSubarray(arr,N)) ` ` `  `# This article is contributed by Shrikant13 `

 `// C# Program to find the Length  ` `// of the largest Subarray with  ` `// only even elements ` `using` `System; ` ` `  `class` `GFG ` `{ ` `// Function to find the Length  ` `// of the largest Subarray with ` `// only even elements ` `static` `int` `maxEvenSubarray(``int` `[]array,  ` `                           ``int` `N) ` `{ ` `    ``int` `ans = 0; ` `    ``int` `count = 0; ` ` `  `    ``// Iterate the loop ` `    ``for` `(``int` `i = 0; i < N; i++)  ` `    ``{ ` `        ``// Check whether the element is ` `        ``// even in continuous fashion ` `        ``if` `(array[i] % 2 == 0) ` `        ``{ ` `            ``count++; ` `            ``ans = Math.Max(ans, count); ` `        ``} ` `        ``else` `        ``{ ` `            ``// If element are not even in ` `            ``// continuous fashion, ` `            ``// Reinitialize the count ` `            ``count = 0; ` `        ``} ` `    ``} ` ` `  `    ``// Check for the last  ` `    ``// element in the array ` `    ``ans = Math.Max(ans, count); ` `    ``return` `ans; ` `} ` ` `  `// Driver Code ` `public` `static` `void` `Main() ` `{ ` `    ``int` `[]arr = { 9, 8, 5, 4,  ` `                  ``4, 4, 2, 4, 1 }; ` ` `  `    ``int` `N = arr.Length; ` ` `  `    ``Console.WriteLine(maxEvenSubarray(arr, N)); ` `} ` `} ` ` `  `// This code is contributed by ihritik `

 ` `

Output:
```5
```

Time Complexity:

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.

Improved By : shrikanth13, ihritik, dharan1011

Practice Tags :