Python Coding Challange - Question with Answer (01300525)

 

What is happening?

This is a recursive function, where the function sum() calls itself.

But it is missing a base case, which is essential in recursion to stop the loop.

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 Step-by-step execution:

• sum(2)
  → returns 2 + sum(1)

• sum(1)
  → returns 1 + sum(0)

• sum(0)
  → returns 0 + sum(-1)

• sum(-1)
  → returns -1 + sum(-2)

• ... and so on, forever...

It keeps calling itself with smaller and smaller numbers and never stops.

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❌ Problem:

There is no base case like:

if num == 0:
    return 0

So Python will eventually stop the program and raise this error:

RecursionError: maximum recursion depth exceeded

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✅ How to fix it?

Add a base case to stop recursion:

def sum(num):
    if num == 0:
        return 0
    return num + sum(num - 1)
print(sum(2)) # Output: 3

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 Summary:

Concept	Explanation
Recursion	Function calling itself
Base Case	Missing → causes infinite recursion
Error Raised	RecursionError
Fix	Add if num == 0: return 0