11: Pointers and Linked Lists

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Questions and Answers

What is a key difference between references and pointers?

References cannot be null.
Pointers can point to no object. (correct)
References can be modified after creation.
Pointers cannot be changed after creation.

A null-pointer can be dereferenced safely without causing an error.

False (B)

What keyword is used to represent a null-pointer in C++?

nullptr

A pointer to an int is declared as _____.

int* Signup and view all the answers

Match the following terms with their definitions:

Pointer = A variable that holds the address of another variable Null-pointer = A special pointer that signals no object points to it Dereferencing = Accessing the value at the address held by a pointer Pointer type = Defined by T* where T is a data type Signup and view all the answers

What will happen if you try to initialize a std::string pointer with an int pointer?

It will result in a compiler error. (B) Signup and view all the answers

Why is it important to check if a pointer is nullptr before dereferencing it?

To avoid undefined behavior and potential runtime errors. Signup and view all the answers

What is a key advantage of using a linked list over a vector?

Easy insertion and deletion of elements (C) Signup and view all the answers

Linked lists provide efficient random access to elements.

False (B) Signup and view all the answers

What is the main component of a linked list?

lnode Signup and view all the answers

A linked list consists of nodes that contain user data and a pointer to the ______.

next element Signup and view all the answers

Match the following terms related to linked lists with their definitions:

lnode = A structure containing user data and a pointer to the next element Insertion = Adding an element to the linked list Deletion = Removing an element from the linked list Head = Pointer to the first element in a linked list Signup and view all the answers

Which of the following describes a linked list?

Supports efficient insertion and deletion (B) Signup and view all the answers

An lnode can only contain an integer value.

False (B) Signup and view all the answers

What does the 'next' pointer in an lnode do?

Points to the next lnode Signup and view all the answers

A linked list does not require a ______ area of memory.

contiguous Signup and view all the answers

What is a potential downside of writing overly compact code?

It may be difficult for others to comprehend. (D) Signup and view all the answers

Using a second pointer, tail, in a list data structure can improve the efficiency of operations like push_back.

True (A) Signup and view all the answers

What mechanism can be implemented to efficiently return the size of a list without traversing it?

Maintain a member variable to keep track of the list size. Signup and view all the answers

In a linked list implementation, the pointer that points to the first element is called the _______.

head Signup and view all the answers

Match the following linked list variations with their advantages or characteristics:

Singly linked list = Simple structure, only one pointer per node Doubly linked list = Allows traversal in both directions Linked list with sentinels = Simplifies edge cases for empty lists Circular linked list = Last node points back to the first node Signup and view all the answers

What is the purpose of the `our_list` class?

To wrap a pointer to the first element and manage list operations. (D) Signup and view all the answers

The `push_front` method modifies the value of the head pointer to point to the newly added node.

True (A) Signup and view all the answers

What does the `print` member function do?

Outputs the value of each element in the linked list. Signup and view all the answers

In the `our_list::push_front` method, the new element is initialized with a value of ______ and the next pointer to the current head.

4 Signup and view all the answers

Match the methods with their functionalities in the `our_list` class:

print = Outputs element values of the linked list push_front = Adds a new node at the front size = Returns the number of elements in the list push_back = Adds a new node at the end Signup and view all the answers

What could happen if the for-loop in the `print` function iterates beyond the valid nodes?

It will result in undefined behavior. (A) Signup and view all the answers

The `head` pointer in the `our_list` class points to the last element of the list.

False (B) Signup and view all the answers

What type is the `next` pointer in the `lnode` structure?

lnode* Signup and view all the answers

The implementation of the `print` function uses a ______ loop to iterate through the linked list.

for Signup and view all the answers

What type of data structure does the `our_list` class represent?

Linked list (C) Signup and view all the answers

What will happen if a new lnode is not allocated dynamically in the push_front method?

It will lead to undefined behavior. (D) Signup and view all the answers

The constructor of our_list initializes the head to nullptr.

True (A) Signup and view all the answers

What should be checked in the push_back implementation before accessing n->next?

Check if head is nullptr. Signup and view all the answers

In the push_back implementation, if the list is not empty, we traverse to the end by using a _________ loop.

for Signup and view all the answers

Match the following implementations with their descriptions:

Example 16.2 = A buggy implementation of push_back Example 16.3 = A correct implementation of push_back Example 16.4 = A compact version using double-pointers Constructor = Initializes the list with a given size Signup and view all the answers

Which case checks for an empty list in the push_back method?

Case 1: Empty list (D) Signup and view all the answers

The implementation of push_back in Example 16.3 handles the empty list case correctly.

True (A) Signup and view all the answers

What is one possible drawback of using the implementation in Example 16.4?

It is less explicit and harder to understand. Signup and view all the answers

The implementation of dynamic data structures requires taking all possible ______ into account.

cases Signup and view all the answers

What is the purpose of the push_front method?

To add an element at the beginning of the list. (D) Signup and view all the answers

What member function of the `our_list` class provides an iterator to the last element plus one?

end() (A) Signup and view all the answers

The `operator[]` in the `our_list` class allows for random access to elements in the list.

False (B) Signup and view all the answers

What does the `operator++` function do in the context of the `our_list` iterator?

Advances the iterator to the next element. Signup and view all the answers

The `our_list::begin()` function returns an iterator pointing to the ______ element.

first Signup and view all the answers

Match the following operations with their descriptions in the context of `our_list`:

begin() = Returns an iterator to the first element. end() = Returns an iterator past the last element. operator*() = Accesses the current element pointed to by the iterator. operator++ = Advances the iterator to the next element. Signup and view all the answers

What is the main issue with the first attempt to create a wagon structure?

The field 'next' has an incomplete type. (A) Signup and view all the answers

A pointer must always be initialized at the time of its declaration.

False (B) Signup and view all the answers

What type does the 'next' member of a wagon in C++ need to be, in order to form a linked list?

wagon* Signup and view all the answers

To create a new wagon in C++, one needs to use the _______ expression.

new Signup and view all the answers

Which of the following examples correctly declares a pointer to an integer?

int* p; (B) Signup and view all the answers

Match the pointer types with their descriptions:

int* = Pointer to an integer std::string* = Pointer to a string wagon* = Pointer to a wagon object void* = Pointer to any type Signup and view all the answers

The 'next' pointer in a wagon structure can point to a newly created wagon or be set to nullptr.

True (A) Signup and view all the answers

What is one advantage of linked lists over vectors in C++?

Dynamic size and efficient insertions/deletions. Signup and view all the answers

What happens if the list is empty when the push_back method is called?

The program results in undefined behavior. (A) Signup and view all the answers

The push_back method handles the empty list case correctly by checking if head is nullptr.

True (A) Signup and view all the answers

What is maintained as a member variable to improve efficiency in getting the size of the list?

count Signup and view all the answers

In the push_back method, the ____ pointer is used to point directly to the last element of the list for efficiency.

tail Signup and view all the answers

What will the size function return if the list is empty?

0 (C) Signup and view all the answers

Dereferencing a nullptr in the push_back implementation will not cause an error.

False (B) Signup and view all the answers

What is the initial value of count when using the simple size implementation?

0 Signup and view all the answers

The push_back method appends a new element to the list by setting n->next to a new lnode containing the value of _____.

e Signup and view all the answers

Which of the following methods is considered inefficient for calculating the size of our_list?

Iterating through the linked list (B) Signup and view all the answers

What does the operator* do in the our_list iterator?

Accesses the current element (C) Signup and view all the answers

The operator++ increases the iterator by one and returns a reference to the iterator itself.

True (A) Signup and view all the answers

What is the purpose of the begin() member function in the our_list class?

To return an iterator pointing to the first element of the list. Signup and view all the answers

An iterator can be compared to another iterator using the operator ______.

!= Signup and view all the answers

Match the iterator functionality with its description:

operator++ = Advances the iterator to the next element operator*() = Accesses the current element value operator!= = Checks if two iterators are not equal Signup and view all the answers

What type of pointer does the lnode structure have?

A pointer to the next lnode (D) Signup and view all the answers

The operator++ method does not need to check if the current node is nullptr.

False (B) Signup and view all the answers

Which of the following describes a key characteristic of a linked list?

Each element points to its successor. (C) Signup and view all the answers

The 'push_front' method allows easy removal of the first element in a linked list.

False (B) Signup and view all the answers

What does the constructor of our_list::iterator initialize its member variable, 'node', to?

It initializes it to the lnode pointer passed as an argument. Signup and view all the answers

What does the 'next' pointer in an lnode structure do?

It points to the next node in the linked list. Signup and view all the answers

The our_list::iterator class is defined as a ______ class within the our_list class.

public inner Signup and view all the answers

In the implementation of the our_list constructor, head is initialized to _____ to indicate an empty list.

nullptr Signup and view all the answers

What does the end() member function of our_list return?

An iterator pointing past the last element (D) Signup and view all the answers

Match the linked list methods with their functionalities:

push_front = Adds an element to the front of the list push_back = Adds an element to the end of the list print = Displays the elements of the list our_list = Constructor for the linked list Signup and view all the answers

What is a disadvantage of using linked lists compared to arrays?

Traversal requires more time due to non-contiguous memory. (B) Signup and view all the answers

Dynamic allocation of nodes is necessary for the 'push_front' method to ensure data isn't lost after method execution.

True (A) Signup and view all the answers

How does the 'print' function identify when to stop traversing the list?

It checks for a nullptr pointer. Signup and view all the answers

The linked list structure includes a node type called _____ that contains an integer value and a pointer to the next node.

lnode Signup and view all the answers

Which operation in linked lists is typically less efficient and requires traversal from the head?

Inserting an element at the end with push_back (C) Signup and view all the answers

What is the purpose of the dereference operator (*) in pointer usage?

To access the value at the memory address the pointer points to (D) Signup and view all the answers

A pointer can point to multiple types of objects at the same time.

False (B) Signup and view all the answers

What keyword is used to initialize a pointer without a starting value?

nullptr Signup and view all the answers

To obtain the address of a variable, the _______ operator is used.

& Signup and view all the answers

Match the pointer operations with their descriptions:

ptr = nullptr = Initializes the pointer without a valid target. *ptr = 5 = Sets the value at the memory location to 5. ptr = &a = Makes the pointer point to the address of variable a. ptr == other_ptr = Compares if both pointers point to the same address. Signup and view all the answers

When declaring a pointer, what must the type of the pointer match?

The type of the variable it will point to (B) Signup and view all the answers

The statement `int* ptr = &a;` is valid if a is an integer variable.

True (A) Signup and view all the answers

What will happen if you try to dereference a nullptr pointer?

It will cause a runtime error. Signup and view all the answers

Flashcards

Null Pointer

A special pointer value indicating that it doesn't point to any object. It's represented by the literal nullptr and can be converted to any pointer type.

Pointers

Pointers allow you to store the memory address of a variable, giving you direct access to its location. They are similar to references but can be modified after creation, meaning their target can change.

Value of a Pointer

The value of a pointer to a data type T is the memory address of an object of type T. This allows you to access and manipulate the object directly.

Null Pointer

A pointer that points to no object. It's denoted by the keyword nullptr and can be assigned to any pointer type.