4.1.1.16 Recursive techniques Quiz: AQA Computer Science, Unit 1

The 20 questions

1. What fundamental action defines a recursive subroutine in programming?

   • Using loops
   • Modifying arrays
   • Calling itself
   • Declaring globals

2. What two essential components must any recursive subroutine contain?

   • Global and local variables
   • Base and recursive cases
   • Procedure and function
   • Loop and counter

3. What is the main purpose of a base case in recursion?

   • Declaring variables
   • Allocating memory
   • Calling the function
   • Stopping the recursion

4. Which expression is the standard recursive definition of factorial for n >= 1?

   • n! = n * n
   • n! = n + (n - 1)!
   • n! = n * (n - 1)!
   • n! = 1 for all n

5. What is 5! (factorial of 5)?

   • 60
   • 25
   • 15
   • 120

6. What does the recursive function fact(n) return when n = 0, given the base case fact(0) = 1?

   • 0
   • 1
   • It loops forever
   • n

7. A recursive function sumTo(n) returns n + sumTo(n - 1) with the base case sumTo(0) = 0. What is sumTo(4)?

   • 10
   • 6
   • 24
   • 4

8. What happens if a recursive function lacks a base case?

   • Infinite recursion
   • Immediate termination
   • Compilation error
   • Syntax failure

9. Which feature makes a problem well suited to recursion?

   • Constant outcomes
   • Linear iteration
   • Self-similar subproblems
   • Sequential inputs

10. What must each recursive step do to ensure termination?

    • Approach base case
    • Loop infinitely
    • Reset stack frames
    • Increase problem size

11. Which memory structure is heavily used by recursion but not iteration?

    • Call stack
    • Disk storage
    • Heap memory
    • Static memory

12. A recursive function counts down from n to 1 and prints each value. What is printed when called with n = 3?

    • 3, 2, 1
    • 3, 3, 3
    • 2, 1
    • 1, 2, 3

13. What is the result of power(2, 3) if power(x, n) = x * power(x, n - 1) with the base case power(x, 0) = 1?

    • 8
    • 5
    • 6
    • 9

14. What must change between successive recursive calls to prevent an infinite loop?

    • Global constants
    • Function names
    • Return types
    • Parameter values

15. What data is stored in the separate stack frame of a recursive call?

    • Global variables
    • Source code
    • Local variables
    • Bytecode instructions

16. A recursive function is used to calculate the sum of the digits of a number. For 123, which result is correct?

    • 3
    • 5
    • 6
    • 123

17. A recursive binary search splits a list in half each call. Roughly how many calls are needed for a list of 1024 items in the worst case?

    • About 2
    • About 10
    • About 512
    • About 1024

18. What part of a recursive function prevents infinite recursion from occurring?

    • Return address
    • General case
    • Stack frame
    • Base case

19. What is the base case when recursively calculating string length?

    • Empty string
    • Single character
    • Full string
    • Null pointer

20. What process passes returned values back through previous recursive subroutines?

    • Heap allocation
    • Stack unwinding
    • Stack pushing
    • Queue popping

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