AP CSA Recursion

Question 1

What is the base case in a recursive method?

Accepted Answer

The condition that stops the recursion

Answer

The base case is the condition that terminates recursion by returning a result without making further recursive calls.

Question 2

What error occurs when a recursive method has no base case or never reaches it?

Accepted Answer

StackOverflowError

Answer

Infinite recursion causes the call stack to fill up, resulting in a StackOverflowError at runtime.

Question 3

What does the following return? `public int f(int n) { if(n==0) return 0; return n + f(n-1); }` called with f(4)?

Accepted Answer

10

Answer

f(4) = 4 + f(3) = 4+3+2+1+0 = 10, computing the sum of integers from 0 to n.

Question 4

In recursion, each method call gets its own set of local variables stored where?

Accepted Answer

On the call stack

Answer

Each recursive call creates a new stack frame on the call stack that holds its own local variables and parameters.

Question 5

Which of the following best describes mutual recursion?

Accepted Answer

Two methods that each call the other

Answer

Mutual recursion occurs when method A calls method B and method B calls method A, forming a cycle.

AP CSA - Advanced Placement Computer Science A Practice Test