How to Find Average of All Elements in a List in C++?

In C++, the STL provides a list container that is a doubly-linked list that allows storing the data in non-continuous memory locations. In this article, we will learn how to find the average of all elements in a list in C++.

Example:

Input:
myList = {10, 20, 30, 40, 50};

Output: 
Average of all elements in the list is : 30

Finding the Average of All Elements in a List in C++

To find the average or mean of all elements in a std::list, we can use the std::accumulate() function to get the sum of all the elements in the list, and then divide the sum by the size of the list that can be found using std::list::size() to get the average of all elements.

Approach

• First, calculate the size of the std::list using the std::list::size() method.
• Check if n is equal to 0 if yes, print the average as 0.
• Now, calculate the sum of all elements in the list using the std::accumulate() function.
• Return the average as sum / n.

C++ Program to Find the Average of All Elements in a List

The following program demonstrates how we can find the average of all elements in a list in C++.

// C++ program to find the average of all elements in a list

#include <iostream>
#include <list>
#include <numeric>
using namespace std;

int main()
{
    // Initializing a list of integers
    list<int> ls = { 10, 20, 30, 40, 50 };

    // size of list
    int n = ls.size();

    if (n == 0)
        cout << "Average of all elements in the list is: "
             << 0 << endl;

    else {
        // sum of the list elements
        double sum = accumulate(ls.begin(), ls.end(), 0.0);

        // average of the list elements
        double avg = sum / n;
        cout << "Average of all elements in the list is: "
             << avg << endl;
    }

    return 0;
}

Average of all elements in the list is: 30

Time Complexity: O(N), where N is the number of elements in the list.
Auxiliary Space: O(1)