Python Coding challenge - Day 581| What is the output of the following Python Code?

 

Code Explanation:

1. Function Definition: mystery(n, acc=0)

def mystery(n, acc=0):

This function is recursive and calculates something (we'll reveal what it is shortly).

n: the main number we're working with.

acc: short for "accumulator", used to keep track of a running total. Default is 0.

2. Base Case: When n == 0

    if n == 0:

        return acc

If n becomes 0, the function returns the accumulated value acc.

This stops the recursion — the base case.

3. Recursive Case: Add n to acc and Recurse

    return mystery(n - 1, acc + n)

If n is not 0:

Subtract 1 from n

Add current n to acc

Call mystery() again with these new values.

4. Call the Function: print(mystery(4))

Let's trace the recursive calls:

Call n acc Computation

mystery(4) 4 0 → mystery(3, 4)

mystery(3, 4) 3 4 → mystery(2, 7)

mystery(2, 7) 2 7 → mystery(1, 9)

mystery(1, 9) 1 9 → mystery(0, 10)

mystery(0, 10) 0 10 → return 10

Final Output

print(mystery(4))  # Output: 10

Output:

10

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