Overview

In this tutorial, we will understand Recursion using Flowgorithm flowchart. In the earlier example using Function, we have noticed that the Main flowchart calls the function. However, a recursive function is a function that calls itself. A function that calls itself is a recursive function.

Mathematical notation for the sum is

$\LARGE Sum = 1 + 2 + 3 + ... + (n-2) + (n-1) + n$

$\LARGE Sum = \sum_{i=1}^{n} i$

Alternatively, we can define the sum series as:

$\LARGE Sum = n + (n-1) + (n-2) + ... + 3 + 2 + 1$

Recursive calls

Let’s design a recursive function to compute the sum of N positive numbers called RSum. Sum of n numbers in recursive format:

Base case: When n= 1 the sum is 1. This is the halting case. We should tell the function to stop the recursive calls.

Recursive case:

RSum = n + RSum(n-1)

This in turn changes to in the next recursion:

RSum = n + (n-1) + RSum(n-2)

and so on until we reach the base case.

Example Flowchart

RSum is the recursive function. The Main function prompts the user for the number N. The Main function invokes the recursive function with the parameter N.

Recursive Flowchart Flowgorithm