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Find the sum of the first half and second half elements of an array

  • Difficulty Level : Basic
  • Last Updated : 11 Jun, 2021

Given an array arr of size N. The task is to find the sum of the first half (N/2) elements and second half elements (N – N/2) of an array.
Examples: 

Input : arr[] = {20, 30, 60, 10, 25, 15, 40} 
Output : 110, 90 
Sum of first N/2 elements 20 + 30 + 60 is 110
Input : arr[] = {50, 35, 20, 15} 
Output : 85, 35

Approach: 
Initialize SumFirst and SumSecond as 0. Traverse the given array and add elements in SumFirst if the current index is less than N/2 otherwise add in SumSecond.
Below is the implementation of the above approach: 

C++




// C++ program to find the sum of the first half
// elements and second half elements of an array
#include <bits/stdc++.h>
using namespace std;
 
// Function to find the sum of the first half
// elements and second half elements of an array
void sum_of_elements(int arr[], int n)
{
    int sumfirst = 0, sumsecond = 0;
 
    for (int i = 0; i < n; i++) {
        // Add elements in first half sum
        if (i < n / 2)
            sumfirst += arr[i];
 
        // Add elements in the second half sum
        else
            sumsecond += arr[i];
    }
 
    cout << "Sum of first half elements is " <<
                                   sumfirst << endl;
 
    cout << "Sum of second half elements is " <<
                                   sumsecond << endl;
}
 
// Driver Code
int main()
{
    int arr[] = { 20, 30, 60, 10, 25, 15, 40 };
 
    int n = sizeof(arr) / sizeof(arr[0]);
 
    // Function call
    sum_of_elements(arr, n);
 
    return 0;
}

Java




// Java program to count pairs
// whose sum divisible by 'K'
import java.util.*;
 
class GFG
{
 
public static void sum_of_elements(int []arr,
                                   int n)
{
    int sumfirst = 0, sumsecond = 0;
     
    for (int i = 0; i < n; i++)
    {
         
        // Add elements in first half sum
        if (i < n / 2)
        {
            sumfirst += arr[i];
        }
         
        // Add elements in the second half sum
        else
        {
            sumsecond += arr[i];
        }
    }
     
    System.out.println("Sum of first half elements is " +
                                             sumfirst);
     
    System.out.println("Sum of second half elements is " +
                                            sumsecond);
}
 
// Driver code
public static void main(String[] args)
{
    int []arr = { 20, 30, 60, 10, 25, 15, 40 };
    int n = arr.length;
     
    // Function call
    sum_of_elements(arr, n);
}
}
 
// This code is contributed by Princi Singh

Python3




# Python3 program to find the sum of
# the first half elements and
# second half elements of an array
 
# Function to find the sum of 
# the first half elements and
# second half elements of an array
def sum_of_elements(arr, n):
 
    sumfirst = 0;
    sumsecond = 0;
 
    for i in range(n):
         
        # Add elements in first half sum
        if (i < n // 2):
            sumfirst += arr[i];
 
        # Add elements in the second half sum
        else:
            sumsecond += arr[i];
             
    print("Sum of first half elements is",
                    sumfirst, end = "\n");
    print("Sum of second half elements is",
                    sumsecond, end = "\n");
 
# Driver Code
arr = [20, 30, 60, 10, 25, 15, 40];
 
n = len(arr);
 
# Function call
sum_of_elements(arr, n);
 
# This code is contributed
# by Akanksha Rai

C#




// C# program to count pairs
// whose sum divisible by 'K'
using System;
 
class GFG
{
    public static void sum_of_elements(int []arr,
                                       int n)
    {
         
    int sumfirst = 0, sumsecond = 0;
 
    for (int i = 0; i < n; i++)
    {
         
        // Add elements in first half sum
        if (i < n / 2)
        {
            sumfirst += arr[i];
        }
         
        // Add elements in the second half sum
        else
        {
            sumsecond += arr[i];
        }
    }
 
    Console.WriteLine("Sum of first half elements is " +
                                              sumfirst);
     
    Console.WriteLine("Sum of second half elements is " +
                                              sumsecond);
}
 
// Driver code
static public void Main ()
{
    int []arr = { 20, 30, 60, 10, 25, 15, 40 };
    int n = arr.Length;
     
    // Function call
    sum_of_elements(arr, n);
}
}
 
// This code is contributed by nidhiva

Javascript




<script>
 
// Javascript program to count pairs
// whose sum divisible by 'K'
 
    function sum_of_elements(arr , n)
    {
        var sumfirst = 0, sumsecond = 0;
 
        for (i = 0; i < n; i++) {
 
            // Add elements in first half sum
            if (i < parseInt(n / 2))
            {
                sumfirst += arr[i];
            }
 
            // Add elements in the second half sum
            else {
                sumsecond += arr[i];
            }
        }
 
        document.write(
     "Sum of first half elements is " + sumfirst+"<br/>"
        );
 
        document.write(
    "Sum of second half elements is " + sumsecond+"<br/>"
        );
    }
 
    // Driver code
     
        var arr = [ 20, 30, 60, 10, 25, 15, 40 ];
        var n = arr.length;
 
        // Function call
        sum_of_elements(arr, n);
 
// This code contributed by umadevi9616
 
</script>
Output: 
Sum of first half elements is 110
Sum of second half elements is 90

 

Time complexity: O(N)
Auxiliary Space: O(1)

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