Question 1

The difference between direct and indirect recursion is

Accepted Answer

A)  direct recursion occurs when a method invokes itself; indirect recursion occurs when there is an intervening method 
B)  indirect recursion occurs when a method invokes itself; direct recursion occurs when there is an intervening method 
C)  direct recursion only occurs with methods declared to be private; indirect recursion can occur with methods declared to be private, protected, or public 
D)  indirect recursion only occurs with methods declared to be private; direct recursion can occur with methods declared to be private, protected, or public 
E)  none of the above 
A)  direct recursion occurs when a method invokes itself; indirect recursion occurs when there is an intervening method 
B)  indirect recursion occurs when a method invokes itself; direct recursion occurs when there is an intervening method 
C)  direct recursion only occurs with methods declared to be private; indirect recursion can occur with methods declared to be private, protected, or public 
D)  indirect recursion only occurs with methods declared to be private; direct recursion can occur with methods declared to be private, protected, or public 
E)  none of the above

Question 2

For the questions below, assume that int[ ] a = {6, 2, 4, 6, 2, 1, 6, 2, 5} and consider the two recursive methods below foo and bar.
public int foo(int[ ] a, int b, int j)
{
if (j < a.length)
if (a[j] != b) return foo (a, b, j+1);
else return foo (a, b, j+1) + 1;
else return 0;
}
public int bar(int[ ] a, int j)
{
if (j < a.length)
return a[I] + bar(a, j+1);
else return 0;
}
-What is the result of calling bar(a, 0);?

Accepted Answer

A)  0 
B)  5 
C)  6 
D)  12 
E)  34 
A)  0 
B)  5 
C)  6 
D)  12 
E)  34

Question 3

Describe the difference(s) between the following two sets of code, neither of which reaches a terminating condition.
public void forever1( )
{
while (True);
}
public void forever2( )
{
forever2( );
}

Accepted Answer

The method forever1 is iterative and so,

Question 4

For the questions below, consider the following representation of grid and the maze code from Chapter 11.
Grid:
1 1 1 1 1 1 0 0
0 0 1 0 0 1 0 0
0 0 1 0 0 1 1 0
0 0 1 1 0 0 1 0
0 0 0 1 1 0 0 0
0 0 0 0 1 1 1 1
Code:
public boolean traverse(int row, int column)
{
if (valid(row, column))
{
boolean done = false;
grid[row][column] = TRIED;
if (row == grid.length - 1 && column == grid[0].length - 1)
done = True;
else
{
done = traverse(row + 1, column);
if (!done) done = traverse(row, column + 1);
if (!done) done = traverse(row - 1, column);
if (!done) done = traverse(row, column - 1);
}
if (done) grid[row][column] = PATH;
}
return done;
}
Assume valid returns True if row and column are >= 0 and <= the grid's row length or column length and the entry at this position = = 1. And assume TRIED = 3 and PATH = 7
-If traverse is first called with traverse(0, 0); what will the first recursive call of traverse be?

Accepted Answer

A)  traverse(0, 0); 
B)  traverse(0, 1); 
C)  traverse(1, 0); 
D)  traverse(1, 1); 
E)  traverse(0, -1); 
A)  traverse(0, 0); 
B)  traverse(0, 1); 
C)  traverse(1, 0); 
D)  traverse(1, 1); 
E)  traverse(0, -1);

Question 5

For the questions below, refer to the following recursive factorial method.
public int factorial(int x)
{
if (x > 1) return x * factorial (x - 1);
else return 1;
}
-What condition defines the base case for this method?

Accepted Answer

A) (x > 1) B) (x = = 1) C) (x = = 0) D) (x <= 0) E) (x <= 1) A) (x > 1) B) (x = = 1) C) (x = = 0) D) (x <= 0) E) (x <= 1)

Question 6

For the questions below, refer to the following recursive factorial method.
public int factorial(int x)
{
if (x > 1) return x * factorial (x - 1);
else return 1;
}
-What is returned if factorial(0) is called?

Accepted Answer

A)  0 
B)  1 
C)  2 
D)  nothing, factorial(0) causes infinite recursion 
E)  nothing, factorial(0) produces a run-time error 
A)  0 
B)  1 
C)  2 
D)  nothing, factorial(0) causes infinite recursion 
E)  nothing, factorial(0) produces a run-time error

Question 7

The following method correctly multiplies two ints so long as both are non-negative:
public int mpy(int a, int b)
{
return (b > 0) ?
 a + mpy(a, b-1) : 0;
}

Accepted Answer

A) True 
 B)False

Question 8

The following method recognizes whether a String parameter consists of a specific pattern and returns True if the String has that pattern, false otherwise. Use this recursive method to answer the questions below.
public boolean patternRecognizer(String a)
{
if (a == null) return false;
else if (a.length( ) = = 1 | | (a.length( ) = = 2 && a.charAt(0) = = a.charAt(1) ) ) return True;
else if (a.length( ) = = 2 && a.charAt(0) != a.charAt(1) ) return false;
else if (a.charAt(0) == a.charAt(a.length( ) - 1))
return patternRecognizer(a.substring(1, a.length( ) - 1));
else return false;
}
-What is a fractal?

Accepted Answer

A)  a portion of a larger structure (a fraction) 
B)  a geometric shape that can be made up of the same pattern repeated at different scales and orientations 
C)  a recursively defined numeric function 
D)  a ratio (a fraction) 
E)  none of the above 
A)  a portion of a larger structure (a fraction) 
B)  a geometric shape that can be made up of the same pattern repeated at different scales and orientations 
C)  a recursively defined numeric function 
D)  a ratio (a fraction) 
E)  none of the above

The difference between direct and indirect recursion is

Describe the difference(s) between the following two sets of code, neither of which reaches a terminating condition. public void forever1( ) { while (True); } public void forever2( ) { forever2( ); }

For the questions below, refer to the following recursive factorial method. public int factorial(int x) { if (x > 1) return x * factorial (x - 1); else return 1; } -What condition defines the base case for this method?

For the questions below, refer to the following recursive factorial method. public int factorial(int x) { if (x > 1) return x * factorial (x - 1); else return 1; } -What is returned if factorial(0) is called?

The following method correctly multiplies two ints so long as both are non-negative: public int mpy(int a, int b) { return (b > 0) ? a + mpy(a, b-1) : 0; }

Introduction

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Using Classes and Objects

Writing Classes

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Exam 12: Recursion

The difference between direct and indirect recursion is

Describe the difference(s) between the following two sets of code, neither of which reaches a terminating condition. public void forever1( ) { while (True); } public void forever2( ) { forever2( ); }

For the questions below, refer to the following recursive factorial method. public int factorial(int x) { if (x > 1) return x * factorial (x - 1); else return 1; } -What condition defines the base case for this method?

For the questions below, refer to the following recursive factorial method. public int factorial(int x) { if (x > 1) return x * factorial (x - 1); else return 1; } -What is returned if factorial(0) is called?

The following method correctly multiplies two ints so long as both are non-negative: public int mpy(int a, int b) { return (b > 0) ? a + mpy(a, b-1) : 0; }

Introduction

Data and Expressions

Using Classes and Objects

Writing Classes

Conditionals and Loops

More Conditionals and Loops

Object-Oriented Design

Arrays

Inheritance

Polymorphism

Exceptions

Collections

Filters