# Sum of n natural numbers in C++

Written by

Juhi Kamdar

To get the sum of n numbers, there can be two cases:

### Method 1 – Sum of n consecutive numbers without an array(using while loop)

Algorithm:

1. Declare a variable `n` to store the number till which we need to find the sum.
2. Prompt the user to enter a value for `n` and store the input in `n`.
3. Declare a variable `sum` and initialize it to 0 to store the sum of the numbers from 1 to `n`.
4. Use a loop to iterate over the numbers from 1 to `n`, adding each number to `sum`.
5. After the loop terminates, print the value of `sum`.

Code:

``````#include <iostream>
using namespace std;

int main()
{
int n, sum = 0;
cout << "Enter number till which you would like to add: ";
cin >> n;
while (n > 0)
{
sum += n;
n--;
}
cout << "\nSum is: " << sum << endl;
return 0;
}

``````

Output:

``````Enter number till which you would like to add: 3

Sum is:6
``````

### Method 2 – Sum of n numbers without an array(using while loop)

Code:

``````#include <iostream>
using namespace std;

int main()
{
int n, sum = 0, number;
cout << "How many numbers do you want to add? ";
cin >> n;
cout << "\nEnter numbers: ";
while (n > 0)
{
cin >> number;
sum += number;
n--;
}
cout << "\nSum is: " << sum << endl;
return 0;
}

``````

Output:

``````How many numbers do you want to add? 7

Enter numbers:
1
2
3
4
5
89
34

Sum is:138
``````

### Method 3: Sum of n numbers in array(using for loop)

Code:

``````#include <iostream>
using namespace std;

int main()
{
int n, sum = 0;
cout << "How many numbers do you want to add? ";
cin >> n;
int arr[n];
cout << "\nEnter numbers: ";
for (int i = 0; i < n; i++)
cin >> arr[i];
for (int i = 0; i < n; i++)
sum += arr[i];
cout << "\nSum is: " << sum << endl;
return 0;
}

``````

Output:

``````How many numbers do you want to add? : 3

Enter numbers:
23
12
54

Sum is:89
``````