Sum of natural numbers using recursion

Given a number n, find sum of first n natural numbers. To calculate the sum, we will use a recursive function recur_sum().

Examples :

Input : 3
Output : 6
Explanation : 1 + 2 + 3 = 6

Input : 5
Output : 15
Explanation : 1 + 2 + 3 + 4 + 5 = 15



Below is code to find the sum of natural numbers up to n using recursion :

C++

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// C++ program to find the 
// sum of natural numbers up
// to n using recursion
#include <iostream>
using namespace std;
  
// Returns sum of first 
// n natural numbers
int recurSum(int n)
{
    if (n <= 1)
        return n;
    return n + recurSum(n - 1);
}
  
// Driver code
int main()
{
    int n = 5;
    cout << recurSum(n);
    return 0;
}

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Java

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// Java program to find the 
// sum of natural numbers up
// to n using recursion
import java.util.*;
import java.lang.*;
  
class GFG
{
  
    // Returns sum of first 
    // n natural numbers
    public static int recurSum(int n)
    {
        if (n <= 1)
            return n;
        return n + recurSum(n - 1);
    }
      
    // Driver code
    public static void main(String args[])
    {
        int n = 5;
        System.out.println(recurSum(n));
    }
}
  
// This code is contributed by Sachin Bisht

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Python

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# Python code to find sum 
# of natural numbers upto
# n using recursion
  
# Returns sum of first
# n natural numbers
def recurSum(n):
    if n <= 1:
        return n
    return n + recurSum(n - 1)
  
# Driver code
n = 5
print(recurSum(n))

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C#

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// C# program to find the 
// sum of natural numbers
// up to n using recursion
using System;
  
class GFG
{
  
    // Returns sum of first 
    // n natural numbers
    public static int recurSum(int n)
    {
        if (n <= 1)
            return n;
        return n + recurSum(n - 1);
    }
      
    // Driver code
    public static void Main()
    {
        int n = 5;
        Console.WriteLine(recurSum(n));
    }
}
  
// This code is contributed by vt_m

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PHP

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<?php
// PHP program to find the
// sum of natural numbers 
// up to n using recursion
  
// Returns sum of first 
// n natural numbers
function recurSum($n)
{
    if ($n <= 1)
        return $n;
    return $n + recurSum($n - 1);
}
  
// Driver code
$n = 5;
echo(recurSum($n));
  
// This code is contributed by Ajit.
?>

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Output :

15 


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