Reference lifetime in C++ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a reference to an integer variable.

C++

int x = 10;
int& ref = [1];

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

A10

Bx

C&x

D*x

Attempts:

3 left

💡 Hint

Common Mistakes

Using the value 10 instead of the variable name.

Using pointer syntax like &x or *x.

A reference must be initialized with a variable name, not a value or pointer.

2fill in blank

medium

Complete the function to return a reference to the first element of the array.

C++

int& firstElement(int arr[]) {
    return [1];
}

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

Aarr[0]

B*arr

Carr

D&arr[0]

Attempts:

3 left

💡 Hint

Common Mistakes

Returning the array name instead of an element.

Returning a pointer instead of a reference.

Returning arr[0] returns a reference to the first element, matching the return type.

3fill in blank

hard

Fill in the blank with the variable name that matches the return statement.

C++

int& getValue() {
    int [1] = 5;
    return value;
}

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

Avalue

Bref

Cnum

Dval

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that does not match the return statement.

Not realizing returning a reference to a local variable causes undefined behavior.

The local variable must match the returned reference name; however, returning a reference to a local variable is unsafe.

4fill in blank

hard

Fill both blanks to create a reference to a string and modify it.

C++

std::string name = "Alice";
std::string& [1] = [2];
[1] = "Bob";
std::cout << name << std::endl;

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

ArefName

Bname

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same name for the reference and the original variable.

Not initializing the reference with the original variable.

The reference variable refName refers to the string variable name, so modifying refName changes name.

5fill in blank

hard

Fill all three blanks to create a function returning a reference and use it correctly.

C++

int& [1](int& x) {
    return [2];
}

int main() {
    int a = 10;
    int& ref = [3](a);
    ref = 20;
    std::cout << a << std::endl;
    return 0;
}

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

AgetRef

Bx

Da

Attempts:

3 left

💡 Hint

Common Mistakes

Mismatching function name between declaration and call.

Returning a copy instead of a reference.

The function getRef returns a reference to x, and calling getRef(a) returns a reference to a, allowing modification.