Common pointer mistakes in C++ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a pointer to an integer.

C++

int [1] ptr;

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

A*

B#

C&&

D&

Attempts:

3 left

💡 Hint

Common Mistakes

Using & instead of * to declare a pointer.

The asterisk (*) is used to declare a pointer variable in C++.

2fill in blank

medium

Complete the code to assign the address of variable x to pointer ptr.

C++

int x = 10;
int* ptr;
ptr = [1]x;

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

A&

B*

C&&

D#

Attempts:

3 left

💡 Hint

Common Mistakes

Using *x instead of &x when assigning to a pointer.

The ampersand (&) operator gives the address of a variable.

3fill in blank

hard

Fix the error in dereferencing the pointer to get the value of x.

C++

int x = 5;
int* ptr = &x;
int value = [1]ptr;

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

A&

Bptr

C->

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using &ptr instead of *ptr to get the value.

The * operator dereferences the pointer to access the value it points to.

4fill in blank

hard

Fill both blanks to correctly allocate and assign memory for an integer pointer.

C++

int* ptr = [1] int;
*ptr = [2];

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

Anew

B5

Cmalloc

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using malloc in C++ without casting or forgetting to assign value.

Use new int to allocate memory and then assign a value to the dereferenced pointer.

5fill in blank

hard

Fill all three blanks to safely delete a dynamically allocated pointer and avoid dangling pointer.

C++

int* ptr = new int(20);
delete [1];
[2] = [3];

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

Aptr

Cnullptr

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to delete allocated memory or not setting pointer to nullptr after deletion.

Use delete ptr; to free memory and then set ptr to nullptr to avoid dangling pointer.