13.12. Multiple Choice Exercises¶
JULY NOVEMBER
-
What are the actual values of
JULandNOV? JUL NOV
-
What do the values of enumerated types map to?
7 11
-
Since we defined
JANto start at 1,JULandNOVmap to 7 and 11. 6 10
-
Take a closer look at our enumerated type definition.
Q-1: What is the output of the code below?
enum Month { JAN = 1, FEB, MAR, APR,
MAY, JUN, JUL, AUG, SEP, OCT, NOV, DEC };
int main() {
Month m1 = JUL;
Month m2 = NOV;
cout << m1 << " " << m2 << endl;
}
summer
-
Although that is the value of
s, is that printed? It’s summer!It’s fall!
-
This would be the correct answer if this
switchstatement worked. It’s summer!It’s fall!It’s winter!Invalid season!
-
Where are the
breakstatements? Compile error.
-
switchstatements can’t be used onstrings.
Q-2: What is the output of the code below?
int main() {
string s = "summer";
switch (s) {
case "spring":
cout << "It's spring!";
break;
case "summer":
cout << "It's summer!";
case "fall":
cout << "It's fall!";
break;
case "winter":
cout << "It's winter!";
default:
cout << "Invalid season!";
break;
}
}
SUMMER
-
Although that is the value of
s, is that printed? It’s summer!It’s fall!
-
Since there is no
breakstatement after the case for summer but there is one after fall, this is correct. It’s summer!It’s fall!It’s winter!Invalid season!
-
Where are the
breakstatements? Compile error.
-
Since
sis an enumerated type, theSeasons are mapped toints, which are valid forswitchstatements.
Q-3: What is the output of the code below?
enum Season { SPRING, SUMMER, FALL, WINTER };
int main() {
Season s = SUMMER;
switch (s) {
case SPRING:
cout << "It's spring!";
break;
case SUMMER:
cout << "It's summer!";
case FALL:
cout << "It's fall!";
break;
case WINTER:
cout << "It's winter!";
default:
cout << "Invalid season!";
break;
}
}
vector<Entry> entries;-
We create a
vectorwith typeEntry. Entry entries-
This only creates one
Entry. vector<Dictionary> Entry-
This creates a
vectorofDictionarys calledEntry. We can’t make an object that contains a
vector.-
We can have
vectors inside objects.
Q-4: Take a look at the struct definition of Entry. If we wanted to make a
struct called Dictionary, how can we create a vector of Entrys
as a member variable?
struct Entry {
string word;
int page;
}
We can’t have a
vectorinDeck.-
We are allowed to have
vectors in objects. The definition of
Card::find()is invalid.-
The definition references
Deck, butDeckis defined afterCard. We can’t define
print()in bothCardand inDeck.-
Although they have the same name, these are two different
print()functions. Nothing is wrong with the code.
-
There is an error in the code. Can you find it?
Q-5: What is wrong with the code below?
struct Card {
int suit, rank;
Card ();
Card (int s, int r);
void print () const;
bool isGreater (const Card& c2) const;
int find (const Deck& deck) const;
};
struct Deck {
vector<Card> cards;
Deck ();
Deck (int n);
void print () const;
int find (const Card& card) const;
};
Our code can’t split the deck exactly in half.
-
We can split the deck exactly in half.
The way our code would shuffle cards would be unpredictable.
-
Part of the problem is that the cards would be shuffled in a predictable manner.
Our code would result in an infinite loop.
-
There’s no reason to loop infinitely.
Our code would perform a perfect shuffle.
-
Because the cards are shuffled perfectly, the exact ordering of the cards is predictable and thus the cards aren’t really shuffled.
Q-6: Why can’t we code our shuffle function to work the exact same way humans shuffle cards?
They are longer than the bigger functions since they do all the work.
-
Most helper functions are shorter than the bigger function.
They are simpler functions that help the bigger function.
-
As the name implies, they help a bigger function.
They shorten the code used in bigger functions.
-
Usually the bigger function has repetitive code, which is then put into a helper function to help shorten the bigger function.
They make debugging easier.
-
Since helper functions break down the bigger function into smaller parts, it’s easier to isolate and identify issues.
Q-7: What is true about helper functions?
Encapsulation
-
This is the process of wrapping up a sequence of instructions in a function.
Generalization
-
This is the process of taking something specific and making it more general.
Top-down design
-
This is the process of using pseudocode to sketch solutions to large problems and design the interfaces of helper functions.
Bottom-up design
-
This is the process of writing small, useful functions and then assembling them into larger solutions.
Q-8: Using pseudocode to figure out what helper functions are needed is a characteristic of what?
Running a for loop too little or too many times.
-
This can lead to too few iterations or too many iterations.
Forgetting that indexing starts at 0.
-
This can lead you to have values that are shifted by one.
Using less than instead of less than or equal to in a while loop.
-
This can lead to running the while loop one less times than what you wanted.
All of the above.
-
These can all lead to off by one errors.
Q-9: Which of the following can lead to off by one errors?
n log n
-
This makes mergeSort faster than our previous version of selection sort.
n!
-
mergeSort runs faster than factorial time.
logn
-
mergeSort runs slower than logarithmic time.
n^2
-
This is the time complexity of selection sort.
Q-10: What is the amount of time that mergeSort takes?
Bubble sort
-
Bubble sort swaps adjacent items and “bubbles” the lightest items to the top.
Insertion sort
-
Insertion sort selects an item from the unsorted section and puts it in the right location in the sorted section.
Selection sort
-
Selection sort finds the smallest item at each iteration i and puts it at the ith location.
Quicksort
-
Quicksort uses recursive calls to partition a list.
Q-11: What kind of sorting algorithm is our sortDeck function? You are encouraged to search up these different sorting algorithms!