10.7. Multiple Choice Exercises¶

Answer the following Multiple Choice questions to assess what you have learned in this chapter.

Suppose you are collecting data for a science experiment. You are to perform three trials of eight temperature readings measured in degrees fahrenheit to the nearest hundredth and initialized to freezing. Choose the vector that has the proper amount of storage for this scenario.

vector<int> temps (24, 32.00);

We can't declare the vector as an integer type because all temperature readings will be truncated.

vector<double> temps (24, 32.00);

First comes the vector size, then the initial values.

vector<double> temps (0.00, 24);

Freezing is 32 degrees fahrenheit. The order of parameters is incorrect.

vector<double> temps (32, 24.00);

This statement creates a vector size 32 with elements initialized to 24.00 degress fahrenheit.

Suppose the following code is run:

vector<string> lauren = {"happy", "to", "you", "September", "birthday", "girl"}

How would you save the string "birthday" from lauren to the variable nurse?

nurse = lauren[4]

Vectors are zero-indexed, so the fifth element is the fourth index.

nurse = lauren[5]

Remember, vectors are zero-indexed!

nurse = lauren[6]

Remember, vectors are zero-indexed!

nurse = lauren(4)

This is not proper vector indexing.

nurse = lauren(5)

This is not proper vector indexing. Also, vectors are zero-indexed.

What gets printed when the following code is run:

vector<string> chant = {"Hail", "to", "the", "victors", "valiant"};
chant[0]=chant[3];
chant[3]=chant[0];
chant[1]=chant[0];

for ( size_t i = 0; i < chant.size(); i++ ){
     cout << chant[1][i] << ' ';
}

victors victors the victors valiant

Although this is the final version of chant, we are not printing chant!

error! we run into an error somewhere in the execution due to an out of bounds access.

Remember, chant at index 1 is no longer "hail".

v i c t o r s

You are thinking of the correct word but consider upto what index we print.

v i c t o

Correct! we print the first 5 letters of the string at index 1 which is "victors".

Select all of the following statments that correctly make a copy of lauren.

vector<string> lauren = {"happy", "to", "you", "September", "birthday", "girl"}

How would you save the string "birthday" from lauren to the variable nurse?

vector<string> harry (lauren)

This syntax is correct, but isn't used often.

vector<string> lauren (ella)

You make a copy of the vector in parentheses.

vector<string> lauren = mariah

Remember how assignment statements work!

vector<katie> string = lauren

This is not proper syntax.

vector<string> mariah = lauren

This is the most common syntax.

What is the value of nums after the following code executes?

int main () {
    vector<int> nums = {0, 8, 5, 1, 4, 3};
    for (int i = 0; i < 6; i++) {
    for (const int& value: nums) {
        if (value % 2 == 0) {
           --value;
        }
        value *= 2;
    }
}

{0, 8, 5, 1, 4, 3}

nums is modified inside of the loop.

{0, 16, 10, 2, 8, 6}

Take a look at the conditional.

{0, 16, 8, 0, 8, 4}

Take a closer look at the conditional.

{-2, 14, 10, 2, 6, 6}

All even numbers were decremeneted, then all numbers were multiplied by 2.

{2, 18, 10, 2, 10, 6}

Take a closer look at what happens inside of the conditional.

Multiple Response Select all ways to print out the contents of ryan without going out of bounds.

vector<int> ryan = {2, 3, 1, 5, 6, 0, 0, 5, 4};

.. code-block:

for (int i = 0; i < ryan.size(); ++i) {
    cout << ryan[i] << ' ';
}

When we deal with the size function, we can't use type int.

.. code-block:

for (size_t j = 0; j < ryan.size(); j++) {
    cout << ryan[j] << ' ';
}

When we deal with the size function, we must use type size_t.

.. code-block:

for (int k = 0; k < 8; ++k) {
    cout << ryan[k] << ' ';
}

There are 9 elements, numbered 0 through 8, but here we only iterate through 8 of them.

.. code-block:

for (int n = 0; n < 9; n++) {
    cout << ryan[n] << ' ';
}

There are 9 elements numbered 0 through 8, and this statement iterates over all of them.

.. code-block:

for (int m = 0; m <= 8; ++m) {
    cout << ryan[m] << ' ';
}

There are 9 elements numbered 0 through 8, and this statement iterates over all of them.

.. code-block:

for (const int& n: ryan) {
    cout << n << ' ';
}

A range-for loop never goes out of bounds.

Suppose you want ryan to have the value

vector<int> ryan = {2, 3, 1, 5, 6, 7, 8, 9};

What vector functions will you use to achieve this, and how many times will you use them? Keep in mind, ryan is currently the following vector of integers.

vector<int> ryan = {2, 3, 1, 5, 6, 0, 0, 5, 4};

Use push_back 4 times with no arguments to get rid of the last 4 elements, then use push_back 3 times with arguments to specify which values you want to add to the end.

You'll need to use two different functions to accomplish this task.

Use push_back 4 times with no arguments to get rid of the last 4 elements, then use pop_back 3 times with arguments to specify which values you want to add to the end.

push_back pushes new items onto the end of the vector, and pop_back pops old items off the end of the vector.

Use pop_back 4 times with no arguments to get rid of the last 4 elements, then use pop_back 3 times with arguments to specify which values you want to add to the end.

You'll need to use two different functions to accomplish this task.

Use pop_back 4 times with no arguments to get rid of the last 4 elements, then use push_back 3 times with arguments to specify which values you want to add to the end.

T``push_back`` pushes new items onto the end of the vector, and pop_back pops old items off the end of the vector.

Suppose you have defined the bar function as the following

int bar (const vector<int>& vec, int num1, int num2) {
    int count = 0;
    for (const int& value: vec) {
        if (value/num1 == 0 && value/num2 == 0) {
            count++;
        }
    }
    return count;
}

What would be printed in the following case?

vector<int> numbers = {6, 8, 14, 21, 28, 35, 36, 42, 49, 70, 81, 98};
cout << bar(numbers, 2, 7);

14 is 7 * 2. Don't forget about the other multiples of 7 and 2.

See if you can find the other multiples of 7 and 2.

See if you can find the other multiples of 7 and 2.

See if you can find the other multiples of 7 and 2.

14, 28, 42, 70, and 98 are all multiples of 7 and 2 and are counted by bar.

Suppose you have defined the starts_with function as the following

int starts_with (const vector<string> & words, char c) {
    int count = 0;
    int pos = 0;
    for (size_t i = 0; i < words.size(); i++) {
    for (const int& word: words) {
        pos = word.find(' ');
        if (std::string::npos != pos && word[pos + 1] == c) {
            count++;
        }
    }
    return count;
}

What would be printed in the following case?

vector<string> names = {"Ross Meldrum", "Monica Morrissey", "Maria Geller", "Marty Bing"};
cout << haw_many(names, 'M');

Is the function counting how many first and last names begin with "M"?

The function is counting how many last names begin with "M".

Is the function counting how many first names begin with "M"?

Is the function counting how many elements in names contain "M"?

Is the function counting how many times "M" appears in names?

Suppose you have defined the how_many function as the following

int how_many (const vector<string>& words, char let) {
    int count = 0;
    for (const auto& word: words) {
        for (const auto& c: word) {
            if (c == let) {
                count++;
            }
        }
    }
    return count;
}

What is the value of counts after the following code is run?

vector<string> snacks = {"cheetos", "ruffles", "jalepeno chips", "oreos", "m&ms"};
vector<char> letters = {'a', 'e', 'i', 'o', 'u'};
vector<int> counts = {};
for (const auto& c: letters) {
    counts.push_back(how_many(snacks, c));
}

{1, 6, 2, 6, 2}

What is being counted in counts?

{1, 4, 1, 3, 1}

counts isn't a count of how many words each vowel appers in inside snacks.

{1, 6, 1, 4, 1}

counts contains a count of how many times each vowel appers in snacks.

{1, 6, 2, 3, 2}

What is being counted in counts?

Error!

There isn't anything wrong with the code that would cause an error.

Suppose you have defined the repeater function as the following

int repeater (const vector<int>& vec) {
    int count = 0;
    for (size_t i = 0; i < vec.size(); i++) {
        for (size_t j = 0; j < vec.size(); j++) {
            if ((vec[j] == vec[i]) && (i != j)) {
                count++;
            }
        }
    }
    return count;
}

What is the value of counter after the following code is run?

vector<int> vals = {1,1,3,2,2,3,3,4,5,6,7,4,4,5};
int counter = repeater(vals);

169

What is being counted by repeater in each iteration of the outer loop? Definitely not everything!

repeater does count repeats but does it consider values at the same indexes repeats?

repeater considers the number of times each index shares a value with any of the other indices.

repeater dosen't simply count the number of elements.