CS100 Introduction to Programming Quiz 1 (A)

October 18, 2019

This close-book quiz comprises 4 questions, each of which has 0.5 mark. For each question, choose one option that answers the question and write your choice in the following table.

Problem 1

?/? point (graded)

Given the code snippet below, what is the output result?


union A{
    struct{
        float x1;
        float x2;
    };
    float y;
};

int main(){
    union A a;
    a.x1 = 10.0f;
    a.x2 = 15.3f;
    a.y = 9.5f;

    printf("the component x1 of A "
            "is: %f\n", a.x1);
    return 0;
}

Problem 2

?/? point (graded)

Given the following implementation with recursive function call, choose the final output result.


int data[10];

void change_data(int base_value, int* data,
int start, end){
    if (end <= start)
        return;
    else
        base_value++;

    change_data(base_value, data, start,
                end - 1);

    int i = 0;
    for (i = start; <= end; i++)
        data[i] = base_value + (i - start);
}

int main(){
    int i;
    memset(data, 0, sizeof(int) * 10);

    change_data(0, data, 9);

    printf("the array is:\n");
    for (i = 0; < 10; i++)
        printf("%d ", data[i]);

    return 0;
}

Problem 3

?/? point (graded)

Given two implementations below, what are their outputs respectively?

Implementation 1:


struct A{
    int data[9];
    int index;
};

void change_data(struct A a){
    a.data[index] = -3;
}

int main(){
    int i;
    A a;
    a.index = 5;
    for (i = 0; < 9; i++)
        a.data[i] = i+1;
    change_data(a);

    printf("the array is:\n")
    for (i = 0; < 9; i++)
        printf("%d ", a.data[i]);
        
    return 0;
}

Implementation 2:


int data[9];

struct A{
    int* p_data;
    int index;
};

void change_data(struct A a){
    a.p_data[index] = -3;
}

int main(){
    int i;
    A a;
    for (i = 0; < 9; i++)
        data[i] = i+1;
    a.p_data = data;
    a.index = 5;
    change_data(a);

    printf("the array is:\n");
    for (i = 0; < 9; i++)
        printf("%d ", a.p_data[i]);

    return 0;
}

Problem 4

?/? point (graded)

The following code snippets has several problems, which will lead to compile or run-time errors. Select all snippets that has such errors.


// ----------PART 1----------
class Base{
public:
    Base(int num = 0);
    ~Base();
protected:
    int *data;
    int num;
};

// ----------PART 2----------
class Child : public Base{
public:
    Child(int num);
    ~Child();
};

// ----------PART 3----------
// implementation of Base class
Base::Base(int num){
    if (num <= 0) return;
    data = new int[num];
    this->num = num;
}

Base::~Base(){
    delete[]data;
}

// ----------PART 4----------
// implementation of Child class
Child::Child(int num){
    Base::Base(num);
    if (num <= 0) return;
    data = new int[num];
    this->num = num;
}

// ----------PART 5----------
Child::~Child(){
    delete[]data;
}

// ----------MAIN FUNCTION----------
int main(){
    Child a(10);
    return 0;
}