Created 01/07/03

Quiz on Recursion with Java

Instructions: For each question, choose the single best answer. Make your choice by clicking on its button. You can change your answers at any time. When the quiz is graded, the correct answers will appear in the box after each question.

1. Which answer is a correct skeleton for a recursive Java method?

A.    

int solution( int N )
{
  if ( base case )
  {
    return something easily computed
  }
  else
  {
    divide problem into pieces
    return something calculated from the solution to each piece  
  }
}

B.    

int solution( int N )
{
  if ( base case )
  {
    return something easily computed
  }
  else
  {
    return solution(N)  
  }
}

C.    

int solution( int N )
{
  divide problem into pieces
  return something calculated from the solution to each piece  
}

D.    

int solution( int N )
{
  divide problem into pieces

  if ( base case )
  {
    return something easily computed
  }
  else
  {
    return something calculated from the solution to each piece  
  }
}

2. Consider square numbers defined as follows (for positive integers): 

square(1) = 1
square(N) = square(N-1) + 2N -1

According to this definition, what is square(3)?

A.    square(3) = square(2) + square(1)

B.    square(3) = square(2) - 2*3 +1

C.    square(3) = square(2) + 2*3 -1

D.    square(3) = square(3) + 2*3 -1

3. Look at square numbers again: 

square(1) = 1
square(N) = square(N-1) + 2N -1

Which Java method below successfully implements this definition?

A.    

int square( int N )
{
  if ( N<1 )
  {
    return 1;
  }
  else
  {
    return N*N;
}

B.    

int square( int N )
{
  if ( N==1 )
  {
    return 1;
  }
  else
  {
    return square(N-1) + 2*N - 1;  
  }
}

C.    

int square( int N )
{
  if ( N=1 )
  {
    return 1;
  }
  else
  {
    return square(N-1) + 2*N - 1;  
  }
}

D.    

int square( int N )
{
  if ( N==1 )
  {
    return 1;
  }
  else
  {
    return square(N);  
  }
}

4. Look at square numbers one more time: 

square(1) = 1
square(N) = square(N-1) + 2N -1

Assume the definition has been implemented correctly. How many activations will there be on the activation chain if main() calls square(5)?

A.    1

B.    3

C.    5

D.    6

5. What are two ways to view recursion?

A.    (i) static view, and (ii) dynamic view.

B.    (i) recursive view, and (ii) iterative view.

C.    (i) math view, and (ii) programming view

D.    (i) code view, and (ii) translation view

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