Real-world modeling in C++ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a class named Car.

C++

class [1] {
public:
    int speed;
};

Drag options to blanks, or click blank then click option'

ACar

BVehicle

CEngine

DDrive

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different class name that doesn't match the problem description.

Forgetting to write the class name after the 'class' keyword.

The class is named Car, so the correct keyword after 'class' is 'Car'.

2fill in blank

medium

Complete the code to add a constructor that sets the speed of the Car.

C++

class Car {
public:
    int speed;
    Car([1] s) {
        speed = s;
    }
};

Drag options to blanks, or click blank then click option'

Abool

Bfloat

Cstring

Dint

Attempts:

3 left

💡 Hint

Common Mistakes

Using float or string instead of int for speed.

Forgetting to specify the type of the constructor parameter.

The speed is an integer, so the constructor parameter should be of type int.

3fill in blank

hard

Fix the error in the method that increases the speed by a given amount.

C++

class Car {
public:
    int speed;
    void accelerate(int amount) {
        speed [1] amount;
    }
};

Drag options to blanks, or click blank then click option'

A+=

B-=

C*=

D/=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-=' which decreases speed instead of increasing.

Using '*=' or '/=' which multiply or divide speed.

To increase speed by amount, use the '+=' operator.

4fill in blank

hard

Fill both blanks to create a method that returns true if the car is moving.

C++

class Car {
public:
    int speed;
    bool isMoving() {
        return speed [1] [2];
    }
};

Drag options to blanks, or click blank then click option'

A>

B0

C==

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of '>' which only checks if speed equals zero.

Using '<' which checks if speed is less than zero, which is not correct here.

The car is moving if speed is greater than 0, so use 'speed > 0'.

5fill in blank

hard

Fill all three blanks to create a method that sets the speed only if the new speed is valid (non-negative).

C++

class Car {
public:
    int speed;
    void setSpeed(int newSpeed) {
        if (newSpeed [1] [2]) {
            speed [3] newSpeed;
        }
    }
};

Drag options to blanks, or click blank then click option'

A>=

B0

C=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' instead of '>=' which excludes zero as valid speed.

Using '==' which checks equality instead of comparison.

Using '+=' instead of '=' which would add instead of set.

We check if newSpeed is greater or equal to 0, then assign it to speed using '='.