# Mystery 2005

**This is an algorithm trace task. No implementation is required.**

Read the following algorithm for the recursive function called Mystery. X( ) is a one-dimensional array.

**(a)** Write down the exact output when the function is called with [2 Marks]

- Output ‘The answer is: ’, Mystery(A( ), 5) if A(1) = 6, A(2) = 10, A(3) = 6, A(4) = 18, A(5) = 15.
- Output ‘The answer is: ’, Mystery(A( ), 5) if A(1)=16, A(2)=18,A(3)=12, A(4)=15, A(5)=18.

**(b)** The function is called with Mystery(A( ), 3) where A(1) = 28, A(2) = 20 and A(3) = 28.

Produce a diagram showing each step of the algorithm and the function calls. [9 Marks]

**(c)** Describe the purpose of the algorithm. [3]

**(d)** Write an iterative algorithm that does the same task as the recursive algorithm. [7]

*This task was worth 21 Marks. It was an algorithm trace task. No implementation is required that originally appeared in OCR 2507 Task 4 Jun 2005. All rights and copyright to OCR. Please refer to the OCR Copyright Statement for further information.*

IMAGE CREDIT: https://www.britishmuseum.org/