12.12. Multiple Choice Exercises

Select all of the true statements.

You can have a vector that stores a vector of objects.

• C++ allows for a variety of different compositions.

In order to check to see if two cards are equal, we can use the == operator.

• We have to write a function that compares two cards.

There is no faster way to search through an unsorted vector than using a linear search.

• If the vector were sorted, then there are faster search methods.

There is no such thing as an empty object.

• All variables are given default values unless otherwise specified by the user.

Check answer

What is the correct way to declare a vector of vectors of ints called vec?

vector<int> vec;

• This declares a vector of ints.

vector<int> vec<int>;

• This is not the proper way to declare vec.

vector<vector<int> vec;

• Close! Look closely at the answer choices again.

vector<vector<int> > vec;

• This is the proper way to declare a vector of vectors of ints.

Check answer

What is the value of card?

struct card {
  int m_suit, m_rank;
  card ();
  card (int s, int r);
};

card::card () {
  m_suit = 0;  m_rank = 0;
}

card::card (int s, int r) {
  m_suit = s;  m_rank = r;
}

int main() {
  card card (2, 8);
}

Ace of Clubs

• How did we define our mapping earlier in the chapter?

8 of Hearts

• card has a suit value of 2 corresponding to Hearts, and a rank value of 8.

King of Hearts

• How did we define our mapping earlier in the chapter?

card does not have a value.

• We initialized card with a suit value of 2 and a rank value of 8.

Check answer

There is an error with the code below. Can you find it?

struct card {
  int m_suit, m_rank;
  card ();
  card (int s, int r);
  void print () const;
};

int main() {
  card card (1,3);
  print (card);
}

card is not a valid card.

• A suit of 1 and a rank of 3 maps to the 3 of Diamonds.

There shouldn't be a semicolon after the struct definition.

• A struct definition always ends with a semicolon.

print is a member function.

• Since print is a member function, we need to use the dot operator.

There is nothing wrong with the code.

• There is an error with the code. Can you find it?

Check answer

What is the output of the code below?

struct card {
  int m_suit, m_rank;
  card ();
  card (int s, int r);
  void print () const;
  bool is_greater (const card& c2) const;
};

int main() {
  card card1 (2,12);
  card card2 (2,2);
  cout << card1.is_greater (card2) << '\n';
}

True

• The output of a bool is either a 0 or 1.

False

• The output of a bool is either a 0 or 1.

0

• Is card1 greater than card2?

1

• The Queen of Hearts is greater than the 2 of Hearts.

Check answer

What is the output of the code below?

struct card {
  int m_suit, m_rank;
  card ();
  card (int s, int r);
  void print () const;
  bool is_greater (const card& c2) const;
};

vector<card> build_deck();

bool equals (const card& c1, const card& c2){
  return (c1.m_rank == c2.m_rank && c1.m_suit == c2.m_suit);
}

void print_deck(const vector<card>& deck);

int find (const card& card, const vector<card>& deck);

int main() {
  vector<card> deck = build_deck();
  card card (3, 13);
  cout << find(card, deck);
}

51

• The card is the King of Spades, which is located at the end of the deck.

52

• Since the vector is size 52, it cannot have an index of 52.

12

• What is the value of card?

-1

• What is the value of card?

Check answer

What is true about deck?

struct card {
  int m_suit, m_rank;
  card ();
  card (int s, int r);
  void print () const;
  bool is_greater (const card& c2) const;
};

vector<card> create_deck() {
  vector<card> deck (12);
  int i = 0;
  for (int m_suit = 0; m_suit <= 3; m_suit++) {
    for (int m_rank = 1; m_rank < 4; m_rank++) {
      deck[i].m_suit = m_suit;
      deck[i].m_rank = m_rank;
      i++;
    }
  }
  return deck;
}

int main() {
  vector<card> deck = create_deck();
}

It contains 12 cards.

• create_deck returns a vector of size 12, corresponding to 12 cards.

The highest rank is 4.

• The rank goes up to but does not include 4.

There are no spades in the deck.

• The suit goes up to and include the suit value 3 which corresponds to spades.

The deck has 3 cards in each suit.

• Each suit has an Ace, 2, and 3.

Check answer

How many times does find_bisect need to call itself in order to find the King of Diamonds?

struct card {
  int m_suit, m_rank;
  card ();
  card (int s, int r);
  void print () const;
  bool is_greater (const card& c2) const;
};

vector<card> build_deck();
bool equals (const card& c1, const card& c2);
void print_deck(const vector<card>& deck);
int find (const card& card, const vector<card>& deck);
int find_bisect (const card& card, const vector<card>& deck, int low, int high);

int main() {
  vector<card> deck = build_deck();
  card card (1, 13);
  cout << find_bisect(card, deck, 0, 51);
}

0

• The King of Diamonds is right in the middle of the deck, so it doesn't need to call itself.

1

• Where is the King of Diamonds located relative to the sorted deck?

3

• Where is the King of Diamonds located relative to the sorted deck?

4

• Where is the King of Diamonds located relative to the sorted deck?

Check answer

We want to write the function find_all_queens, which searches through a deck and prints out the location of all 4 queens in the deck. What should go in the blanks?

struct card {
  int m_suit, m_rank;
  card ();
  card (int s, int r);
  void print () const;
  bool is_greater (const card& c2) const;
};

vector<card> build_deck();
bool equals (const card& c1, const card& c2);
void print_deck(const vector<card>& deck);

void find_all_queens (const vector<card>& deck) {
  for (size_t i = 0; i < deck.____; ++i) {
    if (deck[i].____ == 12) {
      cout << ____ << ' ';
    }
  }
}

int main() {
  vector<card> deck = build_deck();
  find_all_queens (deck);
}

push_back(), suit, i

• What value should i go up to?

size(), rank, i

• These are the correct variables and functions.

size, rank, deck[i]

• We want to print the index, not the card.

front(), suit, deck

• What value should i go up to?

Check answer

What is the process of modeling a complex system with a simplified description in order to suppress unnecessary details while capturing relevant behavior?

Generalization

• Generalization means to take something specific and make it more general.

Encapsulation

• Encapsulation means taking a piece of code and wrapping it up in a function.

Abstraction

• Using this process, we can remove unnecessary details to focus on the more important aspects.

Implementation

• Implementation is the process of taking an idea and making it real.

Check answer