C++ Program To Find Sum of First N Natural Numbers

Natural numbers are those positive whole numbers starting from 1 (1, 2, 3, 4, …). In this article, we will learn to write a C++ program to calculate the sum of the first N natural numbers.

Algorithm

• Initialize a variable sum = 0.
• Run a loop from i = 1 to n.
• Inside the loop, add the value of i to the current value of sum for each iteration.
  • sum = sum + x
• After the loop, the variable sum will hold the sum of the first n natural numbers.

C++ Program to Find the Sum of Natural Numbers

C++

// C++ program to find sum of first
// n natural numbers.
#include <iostream>
using namespace std;

// Returns sum of first n natural
// numbers
int findSum(int n)
{
    int sum = 0;
    for (int i = 1; i <= n; i++)
        sum = sum + i;
    return sum;
}

// Driver code
int main()
{
    int n = 5;
    cout << findSum(n);
    return 0;
}

Output

15

Complexity Analysis

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

Refer to the complete article Program to find the sum of first n natural numbers for optimized methods to find the sum of N natural numbers.