Sum of even numbers at even position
Given an array of size n. The problem is to find the sum of numbers that 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)
Approach: Using List comprehension in python and Bitwise & operator
This method uses a list comprehension to create a new list of the even numbers at even indices in the array, and then we use the sum() function to calculate the sum of the numbers.
Python3
# python 3 implementation to # find sum of even numbers # at even indices # Driver program to test above arr = [ 5 , 6 , 12 , 1 , 18 , 8 ] n = len (arr) #using list comprehension to find even values at even indices even_sum = sum ([arr[i] for i in range ( 0 ,n, 2 ) if arr[i] & 1 ! = 1 ]) #printing output print ( "Sum of even numbers at" , "even indices is" , even_sum) # This code is contributed by tvsk |
Output
Sum of even numbers at even indices is 30
Time Complexity: O(n)
Auxiliary Space: O(1)
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