# Sum of even numbers at even position

Given an array of size n. The problem is to find the sum of numbers which are even and are at even index.

**Examples:**

Input : arr[] = {5, 6, 12, 1, 18, 8} Output : 30 Explanation: Here, n = 6 Now here are index and numbers as: index->arr[index] 0->5, 1->6, 2->12, 3->1, 4->18, 5->8 so, number which are even and are at even indices are: 2->12, 4->18 sum = 12+18 = 30 Input : arr[] = {3, 20, 17, 9, 2, 10, 18, 13, 6, 18} Output : 26 Explanation: Here, n = 10 Now here are index and numbers as: index->arr[index] 0->3, 1->20, 2->17, 3->9, 4->2, 5->10, 6->18, 7->13, 8->6, 9->18 So, number which are even and are at even indices are: 4->2, 6->18, 8->6 sum = 2+18+6 = 26

**Implementation:**

## C++

`// C++ implementation to` `// find sum of even numbers` `// at even indices` `#include <bits/stdc++.h>` `using` `namespace` `std;` `// Function to calculate sum` `// of even numbers at even indices` `int` `sum_even_and_even_index(` ` ` `int` `arr[], ` `int` `n) {` ` ` `int` `i = 0, sum = 0;` ` ` ` ` `// calculating sum of even` ` ` `// number at even index` ` ` `for` `(i = 0; i < n; i+=2) {` ` ` ` ` `if` `(arr[i] % 2 == 0) {` ` ` ` ` `sum += arr[i];` ` ` `}` ` ` `}` ` ` ` ` `// required sum` ` ` `return` `sum;` `}` `// Driver program to test above` `int` `main() {` ` ` `int` `arr[] = {5, 6, 12, 1, 18, 8};` ` ` `int` `n = ` `sizeof` `(arr) / ` `sizeof` `(arr[0]);` ` ` `cout << ` `"Sum of even numbers at even indices is "` ` ` `<< sum_even_and_even_index(arr, n);` ` ` ` ` `return` `0;` `}` |

## Java

`// Java implementation to find sum of` `// even numbers at even indices` `import` `java.io.*;` `class` `GFG {` ` ` ` ` `// Function to calculate sum` ` ` `// of even numbers at even indices` ` ` `static` `int` `sum_even_and_even_index(` ` ` `int` `arr[], ` `int` `n)` ` ` `{` ` ` ` ` `int` `i = ` `0` `, sum = ` `0` `;` ` ` ` ` `// calculating sum of even` ` ` `// number at even index` ` ` `for` `(i = ` `0` `; i < n; i+=` `2` `) {` ` ` ` ` `if` `(arr[i] % ` `2` `== ` `0` `) {` ` ` `sum += arr[i];` ` ` `}` ` ` `}` ` ` ` ` `// required sum` ` ` `return` `sum;` ` ` `}` ` ` `// Driver program to test above` ` ` `public` `static` `void` `main (String[] args) {` ` ` ` ` `int` `arr[] = {` `5` `, ` `6` `, ` `12` `, ` `1` `, ` `18` `, ` `8` `};` ` ` `int` `n = arr.length;` ` ` `System.out.println(` `"Sum of even numbers"` ` ` `+ ` `" at even indices is "` `+` ` ` `+ sum_even_and_even_index(arr, n));` ` ` `}` `}` `// This code is contributed by vt_m.` |

## Python3

`# python 3 implementation to` `# find sum of even numbers` `# at even indices` `# Function to calculate sum` `# of even numbers at even indices` `def` `sum_even_and_even_index(arr,n):` ` ` ` ` `i ` `=` `0` ` ` `sum` `=` `0` ` ` `# calculating sum of even` `# number at even index` ` ` `for` `i ` `in` `range` `(` `0` `,n,` `2` `):` ` ` `if` `(arr[i] ` `%` `2` `=` `=` `0` `) :` ` ` `sum` `+` `=` `arr[i]` ` ` ` ` `# required sum` ` ` `return` `sum` `# Driver program to test above` `arr ` `=` `[` `5` `, ` `6` `, ` `12` `, ` `1` `, ` `18` `, ` `8` `]` `n ` `=` `len` `(arr)` `print` `(` `"Sum of even numbers at "` `,` ` ` `"even indices is "` `,` ` ` `sum_even_and_even_index(arr, n))` ` ` `# This code is contributed by Sam007` |

## C#

`// C# implementation to find sum of` `// even numbers at even indices` `using` `System;` `class` `GFG {` ` ` ` ` `// Function to calculate sum` ` ` `// of even numbers at even indices` ` ` `static` `int` `sum_even_and_even_index(` ` ` `int` `[]arr, ` `int` `n)` ` ` `{` ` ` ` ` `int` `i = 0, sum = 0;` ` ` ` ` `// calculating sum of even` ` ` `// number at even index` ` ` `for` `(i = 0; i < n; i+=2) {` ` ` ` ` `if` `(arr[i] % 2 == 0) {` ` ` ` ` `sum += arr[i];` ` ` `}` ` ` `}` ` ` ` ` `// required sum` ` ` `return` `sum;` ` ` `}` ` ` `// Driver program to test above` ` ` `public` `static` `void` `Main () {` ` ` ` ` `int` `[]arr = {5, 6, 12, 1, 18, 8};` ` ` `int` `n = arr.Length;` ` ` `Console.WriteLine(` `"Sum of even numbers"` ` ` `+ ` `" at even indices is "` `+` ` ` `+ sum_even_and_even_index(arr, n));` ` ` `}` `}` `//This code is contributed by vt_m.` |

## PHP

`<?php` `// PHP implementation to` `// find sum of even numbers` `// at even indices` `// Function to calculate sum` `// of even numbers at even indices` `function` `sum_even_and_even_index(` `$arr` `, ` `$n` `)` `{` ` ` `$i` `= 0; ` `$sum` `= 0;` ` ` ` ` `// calculating sum of even` ` ` `// number at even index` ` ` `for` `(` `$i` `= 0; ` `$i` `< ` `$n` `; ` `$i` `=` `$i` `+2) {` ` ` ` ` `if` `(` `$arr` `[` `$i` `] % 2 == 0) {` ` ` ` ` `$sum` `+= ` `$arr` `[` `$i` `];` ` ` `}` ` ` `}` ` ` ` ` `// required sum` ` ` `return` `$sum` `;` `}` `// Driver Code` `{` ` ` `$arr` `= ` `array` `(5, 6, 12, 1, 18, 8);` ` ` `$n` `= sizeof(` `$arr` `) / sizeof(` `$arr` `[0]);` ` ` `echo` `"Sum of even numbers at "` `.` ` ` `"even indices is "` `,` ` ` `sum_even_and_even_index(` `$arr` `, ` `$n` `);` ` ` ` ` `return` `0;` `}` `// This code is contributed by nitin mittal.` `?>` |

## Javascript

`<script>` `// Javascript implementation to` `// find sum of even numbers` `// at even indices` `// Function to calculate sum` `// of even numbers at even indices` `function` `sum_even_and_even_index(` ` ` `arr, n) {` ` ` `let i = 0, sum = 0;` ` ` ` ` `// calculating sum of even` ` ` `// number at even index` ` ` `for` `(i = 0; i < n; i += 2)` ` ` `{` ` ` `if` `(arr[i] % 2 == 0)` ` ` `{ ` ` ` `sum += arr[i];` ` ` `}` ` ` `}` ` ` ` ` `// required sum` ` ` `return` `sum;` `}` `// Driver code` ` ` `let arr = [5, 6, 12, 1, 18, 8];` ` ` `let n = arr.length;` ` ` `document.write(` `"Sum of even numbers at even indices is "` ` ` `+ sum_even_and_even_index(arr, n));` ` ` `// This code is contributed by Mayank Tyagi` `</script>` |

**Output**

Sum of even numbers at even indices is 30

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