Write a recursive function to compute sum of first n integers starting with 1.

// here is code in C++.

#include <bits/stdc++.h>

using namespace std;

// recursive function to find sum from 1 to n

int recur_Sum(int n)

{ // base condition

if (n <= 1)

 return n;

// recursive call

return n + recur_Sum(n - 1);

}

// main function

int main()

{

   // variables

   int n;

   cout<<"Enter a number:";

   // read the number

   cin>>n;

   // print the sum

   cout<<"Sum of first "<<n<<" integer from 1 to "<<n<<" is:"<<recur_Sum(n);

return 0;

}

Explanation:

Read a number from user and assign it to variable "n".Call function recur_Sum() with parameter "n".This function will recursively call itself and find the Sum of first n numbers from 1 to n.Then function will return the sum.

Output:

Enter a number:10

Sum of first 10 integer from 1 to 10 is:55