Linked Lists: Singly, Doubly, Circular

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Questions and Answers

In a doubly linked list, what pointers does each node contain?

  • A pointer to the previous node only.
  • Pointers to both the next and previous nodes. (correct)
  • No pointers, only data.
  • A pointer to the next node only.

Which of the following is a consequence of not freeing memory occupied by a node in a linked list?

  • A memory leak, gradually depleting available memory. (correct)
  • Improved program performance due to memory caching.
  • Faster data access within the linked list.
  • Automatic garbage collection of unused nodes.

In a singly linked list, what does the next pointer of the last node typically point to?

  • A special 'end' node.
  • A random memory location.
  • NULL, indicating the end of the list. (correct)
  • The first node (head) of the list.

What is the primary characteristic that distinguishes a circular linked list from a singly linked list?

<p>The last node in a circular linked list points back to the head. (B)</p> Signup and view all the answers

Which operation is essential before inserting a new node in the middle of a singly linked list?

<p>Traversing the list to find the correct insertion point. (C)</p> Signup and view all the answers

When deleting a node from the end of a singly linked list, what must be updated?

<p>The <code>next</code> pointer of the second to last node must be set to NULL. (B)</p> Signup and view all the answers

What is the role of the new operator in the context of linked lists?

<p>To allocate memory for a new node dynamically. (C)</p> Signup and view all the answers

Which type of linked list allows traversal in both forward and backward directions?

<p>Doubly linked list (D)</p> Signup and view all the answers

What happens if you lose the reference to the head node of a singly linked list?

<p>The list becomes inaccessible, leading to a memory leak if not handled properly. (A)</p> Signup and view all the answers

Which of the following is NOT a standard operation typically performed on linked lists?

<p>Compilation (B)</p> Signup and view all the answers

What key advantage do doubly linked lists provide over singly linked lists in terms of traversal?

<p>The ability to traverse the list in both forward and backward directions. (A)</p> Signup and view all the answers

In a circular linked list, what condition determines the end of a complete traversal?

<p>Returning to the starting node of the traversal. (B)</p> Signup and view all the answers

When inserting a new node in the middle of a doubly linked list, what pointer updates are required?

<p>The <code>next</code> and <code>prev</code> pointers of the new node, the <code>next</code> pointer of the preceding node, and the <code>prev</code> pointer of the following node. (A)</p> Signup and view all the answers

What is the immediate consequence of failing to update the next pointer of the second-to-last node when deleting the last node in a singly linked list?

<p>The list traversal will end prematurely, before the intended second-to-last node. (C)</p> Signup and view all the answers

What is the purpose of the delete operator in the context of linked list memory management?

<p>To remove a node from the linked list and free the memory it occupies. (D)</p> Signup and view all the answers

What is the time complexity of traversing a singly linked list to find a specific node in the worst case scenario?

<p>$O(n)$ (C)</p> Signup and view all the answers

How does the memory allocation strategy in linked lists contribute to their flexibility compared to arrays?

<p>Linked lists allocate memory dynamically, allowing them to grow or shrink as needed without predefining size. (A)</p> Signup and view all the answers

In a doubly linked list, if a node X is to be deleted, what is the correct sequence of pointer updates to maintain list integrity?

<p>Set <code>X-&gt;next-&gt;prev = X-&gt;prev</code> and <code>X-&gt;prev-&gt;next = X-&gt;next</code> before deleting <code>X</code>. (C)</p> Signup and view all the answers

Consider a scenario where you need to implement a data structure that requires frequent insertions and deletions at both ends. Which type of linked list would be most suitable?

<p>Doubly linked list (B)</p> Signup and view all the answers

You have a singly linked list and need to find the node located exactly in the middle. What is an efficient approach to achieve this?

<p>Use two pointers, one moving one node at a time and another moving two nodes at a time. When the faster pointer reaches the end, the slower pointer will be at the middle. (C)</p> Signup and view all the answers

Flashcards

Linked List

A linear data structure where each element is stored in a node, containing data and a pointer to the next node.

Singly Linked List

Each node contains data and a pointer to the next node. Traversal is only possible in one direction.

Doubly Linked List

Each node contains data, a pointer to the next node, and a pointer to the previous node, allowing traversal in both directions.

Circular Linked List

The last node's next pointer points back to the first node, forming a loop.

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Linked List Insertion

Adding a new node to the list, at the beginning, end, or in the middle.

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Linked List Deletion

Removing a node from the list, can occur at the beginning, the end, or in the middle.

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Linked List Traversal

Visiting each node in the list in sequence, starting from the head node.

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Linked List Memory Allocation

Allocate memory for new nodes, done using the new operator.

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Linked List Memory Deallocation

Free the memory occupied by a node when it is no longer needed, done using the delete operator.

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Memory Leak

Occurs when allocated memory is not freed, leading to a gradual depletion of available memory.

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Head Node

The first node in a linked list; serves as the entry point for traversal.

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Circular Traversal

A linked list where traversal can begin at any node and continue indefinitely.

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Pointer Updating

Modifying pointers of the previous and next nodes during insertion or deletion of nodes.

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Dynamic Allocation

Using the new operator to assign space in memory for nodes within a linked list.

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Efficient Memory Management

Crucial process to prevent memory leaks and ensure efficient resource utilization.

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Study Notes

  • Data structures are ways to organize and store data in a computer so that it can be used efficiently
  • A linked list is a linear data structure where elements are stored in nodes
  • Each node contains data and a pointer (or link) to the next node in the sequence
  • Linked lists are dynamic, meaning their size can change during program execution
  • Linked lists are a fundamental data structure in C++

Singly Linked Lists

  • A singly linked list is the simplest type of linked list
  • Each node contains data and a pointer to the next node
  • The first node is called the head
  • The last node's pointer points to NULL, indicating the end of the list, or nullptr
  • Traversal can only be done in one direction, from the head to the tail
  • Traversal is unidirectional, from head to tail

Doubly Linked Lists

  • In a doubly linked list, each node contains data, a pointer to the next node, and a pointer to the previous node
  • This allows traversal in both directions (forward and backward)
  • The first node's previous pointer and the last node's next pointer are NULL
  • Doubly linked lists require more memory due to the additional pointer in each node

Circular Linked Lists

  • A circular linked list is a variation where the last node's next pointer points back to the first node (or head)
  • This forms a circle, and there is no end to the list
  • Traversal can start from any node and continue around the list
  • No node contains a nullptr pointer
  • Traversal can begin at any node and continue indefinitely

Operations on Linked Lists

  • Insertion: Adding a new node to the list
  • Deletion: Removing a node from the list
  • Traversal: Visiting each node in the list in sequence
  • Searching: Finding a specific node in the list
  • Display: Printing all data elements in the linked list.

Insertion

  • Insertion involves adding a new node to the linked list
  • Insertion at the beginning (head): The new node becomes the new head, and its next pointer points to the old head.
  • Insertion at the end (tail): The new node is added after the last node, and the last node's next pointer points to the new node.
  • Insertion in the middle: The new node is inserted between two existing nodes by adjusting the pointers of the surrounding nodes
  • Inserting in middle requires traversal to the node just before where insertion should occur
  • Insertion at the beginning means modifying the head to the new node and having the new node point to the previous head
  • Insertion at the end means traversing to the last node and appending the new node
  • Insertion in the middle means finding the node after which insertion should happen and updating pointers of the previous and the next node
  • Insertion in doubly linked lists requires updating pointers of the previous and next nodes

Deletion

  • Deletion involves removing a node from the linked list
  • Deletion at the beginning (head): The head pointer is moved to the next node, and the old head node is removed from memory
  • Deletion at the end (tail): The next pointer of the second to last node is set to NULL, and the last node is removed from memory
  • Deletion in the middle: The next pointer of the node before the deleted node is updated to point to the node after the deleted node, and the node is removed from memory
  • Deleting in middle requires traversal to the node just before where deletion should occur
  • Deletion at the beginning means making the second node the new head
  • Deletion at the end means traversing to the second-to-last node and setting its next pointer to nullptr
  • Deletion in the middle means updating the pointers of the adjacent nodes to bypass the node being deleted
  • Deletion in doubly linked lists requires updating pointers of the previous and next nodes

Traversal

  • Traversal involves visiting each node in the list in sequence
  • Starting from the head node, follow the next pointers until you reach the end of the list (NULL in singly linked lists or the head again in circular linked lists)
  • During traversal, you can perform operations on each node, such as printing its data or searching for a specific value
  • In a singly linked list, start at the head and follow the next pointers until nullptr is reached
  • In a doubly linked list, traversal can occur in both directions using next and prev pointers
  • In a circular linked list, traversal continues until the starting node is reached again

Memory Management

  • Linked lists use dynamic memory allocation to create and destroy nodes
  • new operator is used to allocate memory for a new node.
  • delete operator is used to free the memory occupied by a node when it is no longer needed
  • Proper memory management is essential to prevent memory leaks
  • Memory leaks occur when allocated memory is not freed, leading to a gradual depletion of available memory
  • Linked lists dynamically allocate memory for each node
  • new operator is used to allocate memory for new nodes
  • delete operator is used to free memory when nodes are removed to prevent memory leaks
  • Memory management is crucial to avoid memory leaks and ensure efficient resource utilization

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