Program to Find the Sum of all Array Elements in C++.

Example 1: 
Input: arr[] = {2, 5, 9, 7, 10}
Output: 33
Explanation: 2 + 5 + 9 + 7 + 10 = 33

Example 2: 
Input: arr[] = {5, -2, 10, 7, 2}
Output: 22
Explanation: 5 + (- 2) + 10 + 7 + 2 = 22

• Declare one sum variable to store the sum of the array and initialize it with 0.  
• Run a for loop through all the array elements and keep on adding them one by one to sum the variable.(sum = sum + arr[i])
• Print the value of the sum. 

//C++ Program to find sum of array elements
#include<iostream>
using namespace std;

//Function to return sum of array
int sum(int arr[], int n){
    int sum = 0;

    for(int i = 0; i < n; i++){
        sum = sum + arr[i];
    }

    return sum;
}

int main(){
    int arr[] = {2, 5, 9, 7, 10};
    //size of given array
    int n = sizeof(arr)/sizeof(arr[0]);

    cout<<"Sum of Array Elements: "<<sum(arr, n);
}

Sum of Array Elements: 33

//C++ Program to find sum of array elements
#include<iostream>
using namespace std;

//Recursive Function to return sum of array
int sum(int arr[], int n){
    //base case
    if(n == 0){
        return 0;
    }
    else{
        //Calling the function recursively
        return arr[0] + sum(arr+1, n-1);
    }
}

int main(){
    int arr[] = {2, 5, 9, 7, 10};
    //size of given array
    int n = sizeof(arr)/sizeof(arr[0]);

    cout<<"Sum of Array Elements: "<<sum(arr, n);
}