Why references are needed in C++ - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

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

C++

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

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

Ar

Bptr

Cref

Dval

Attempts:

3 left

💡 Hint

Common Mistakes

Using a pointer syntax instead of a reference.

Forgetting the ampersand (&) in the declaration.

The code declares r as a reference to the integer variable x.

2fill in blank

medium

Complete the code to modify the original variable through its reference.

C++

int a = 5;
int& ref = a;
ref [1] 10;
// Now a should be 10

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

A=

B+=

C-=

D*=

Attempts:

3 left

💡 Hint

Common Mistakes

Using an arithmetic operator instead of assignment.

Not understanding that the reference acts like the original variable.

Assigning 10 to ref changes the original variable a to 10.

3fill in blank

hard

Fix the error in the function parameter to accept a reference.

C++

void increment([1] num) {
    num++;
}

int main() {
    int x = 3;
    increment(x);
    // x should become 4
}

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

Aint

Bconst int&

Cint*

Dint&

Attempts:

3 left

💡 Hint

Common Mistakes

Passing by value, which does not modify the original variable.

Using a pointer without dereferencing inside the function.

Using int& allows the function to modify the original variable x.

4fill in blank

hard

Fill both blanks to create a function that swaps two integers using references.

C++

void swap([1]& x, [2]& y) {
    int temp = x;
    x = y;
    y = temp;
}

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Avoid

Bint

Cconst

Dauto

Attempts:

3 left

💡 Hint

Common Mistakes

Using void& or const int& which prevents modification.

Using pointers instead of references.

The function parameters must be references to int to swap the original values.

5fill in blank

hard

Fill all three blanks to create a function that returns a reference to the larger of two integers.

C++

int& max([1]& a, [2]& b) {
    return (a [3] b) ? a : b;
}

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

Aconst

Bint

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using const int& which prevents returning a modifiable reference.

Using the wrong comparison operator.

The function returns a reference to the larger integer by comparing a and b.