Data Structure Unit 3: Linked List

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Questions and Answers

What is the primary advantage of using a linked list over an array?

Performance in fixed-size data access
Efficiency in insertion and deletion of elements (correct)
Memory allocation for non-linear data
Support for multi-dimensional data structures

In a singly linked list, what does the 'next' field of a node point to?

The last node in the sequence
The previous node in the sequence
The following node in the sequence (correct)
The first node in the sequence

In a doubly linked list, what is the purpose of the 'prev' field?

To point to the next node only
To point to the previous node in the sequence (correct)
To maintain the order of elements
To mark the end of the list

What typically happens in the last node of a linked list?

It contains a null reference in the link field (D) Signup and view all the answers

Which of the following is NOT a typical use case for linked lists?

Storing fixed-size arrays (B) Signup and view all the answers

Which term is commonly used to refer to the first node in a linked list?

Head (C) Signup and view all the answers

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

Doubly linked list (D) Signup and view all the answers

In the context of Lisp, what is the term used for the payload of the head node?

car (D) Signup and view all the answers

What characterizes a circular linked list?

The last node is linked back to the first node. (B) Signup and view all the answers

What is stored in the LINK array of a linked list?

The pointers to the next nodes. (A) Signup and view all the answers

Which operation involves accessing all elements of the linked list only once?

Traversing (B) Signup and view all the answers

When elements in a linked list are unsorted, what is a major disadvantage of searching?

It is time-consuming due to many comparisons. (D) Signup and view all the answers

What happens during the searching operation in a sorted linked list?

Search stops as soon as a larger element is found. (C) Signup and view all the answers

Which of the following describes an advantage of searching in a sorted linked list?

It requires fewer comparisons. (A) Signup and view all the answers

What does the pointer variable HEAD represent in a linked list?

The first location of the linked list. (D) Signup and view all the answers

What is a significant disadvantage when maintaining a sorted linked list?

The list must be sorted after every insertion or deletion. (C) Signup and view all the answers

What does a null pointer signify in a linked list's context?

The end of the list. (D) Signup and view all the answers

Inserting a new node in a linked list typically requires:

Identifying the correct position for insertion. (C) Signup and view all the answers

What is the purpose of the avail list in a linked list?

To provide memory space for new nodes (C) Signup and view all the answers

Which step is NOT involved in inserting a new node at the start of a linked list?

Find the location of the new node (C) Signup and view all the answers

When inserting a node in a sorted linked list, which condition must be checked first?

If the item to be inserted is less than the first node (B) Signup and view all the answers

What do you check for when deleting the first node in a linked list?

If START is NULL (C) Signup and view all the answers

In the process of deletion of the last node, which pointer is NOT used?

NEXT (C) Signup and view all the answers

What happens when trying to delete a specific node but the linked list is empty?

A message indicates the linked list is empty (A) Signup and view all the answers

What is the final action after successfully inserting a new node in the linked list?

Exit the operation (D) Signup and view all the answers

What condition is checked to verify that a linked list is not overflowing before insertion?

If the available list is not empty (C) Signup and view all the answers

In order to delete the last node, which of the following steps must be performed?

Set START to NULL if it is the only node (B) Signup and view all the answers

Which of the following statements about inserting nodes is correct?

New nodes can be inserted at any position in the list. (D) Signup and view all the answers

What is the primary advantage of using a doubly linked list over a singly linked list?

Allows traversal in both directions (A) Signup and view all the answers

What happens to the pointers when deleting a node from a doubly linked list?

Both backward and forward pointers of the adjacent nodes are updated (C) Signup and view all the answers

In a circular linked list, what is the key characteristic of the last node's link?

Points to the first node of the list (B) Signup and view all the answers

What is a ground header list in the context of linked lists?

Has a last node that points to null (D) Signup and view all the answers

In the deletion algorithm of a doubly linked list, what is done first?

Change the pointer of the next node to bypass the node being deleted (C) Signup and view all the answers

What is the purpose of the AVAIL list in the insertion algorithm?

To keep track of deleted nodes (D) Signup and view all the answers

Which part of a node in a doubly linked list stores data?

INFO (A) Signup and view all the answers

What does the INSTWL algorithm check for at the beginning?

If the AVAIL list is empty (A) Signup and view all the answers

How does a circular header list differ from a grounded header list?

The last node points back to the header node (D) Signup and view all the answers

What is one disadvantage of using a doubly linked list compared to a singly linked list?

Higher memory usage due to additional pointers (B) Signup and view all the answers

What function in C is used to dynamically allocate memory and initializes each block with a default value of '0'?

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

What is one of the key differences between malloc() and calloc()?

malloc() initializes memory with garbage values. (D) Signup and view all the answers

Which syntax is correct for freeing dynamically allocated memory in C?

free(ptr); (B) Signup and view all the answers

What does the realloc() function do in C?

Changes the size of previously allocated memory. (A) Signup and view all the answers

What is a common problem when manually managing memory in languages like C?

Memory leaks from forgetting to free memory. (B) Signup and view all the answers

What is the primary role of garbage collection in programming languages like C# and Java?

To prevent memory leaks by automatically deallocating unused memory. (D) Signup and view all the answers

When reallocating memory using realloc(), what happens to the previously stored values?

They remain unchanged unless the pointer is modified. (C) Signup and view all the answers

Which of the following is NOT a benefit of using garbage collection?

Allowing manual memory management for efficiency. (A) Signup and view all the answers

The parameters used in calloc() include the number of elements and what else?

The size of each element. (A) Signup and view all the answers

What potential issue can arise from freeing memory without modifying a corresponding pointer?

Dangling pointers that can lead to program crashes. (B) Signup and view all the answers

What distinguishes a doubly circular linked list from a standard doubly linked list?

There is no NULL value in the previous field of the node. (B) Signup and view all the answers

Which of the following best describes the purpose of the malloc() function in C?

Allocates a memory block without initializing it. (A) Signup and view all the answers

When traversing a singly linked list, which of the following statements is true?

The traversal stops when ptr reaches NULL. (D) Signup and view all the answers

What action is taken when the pointer (ptr) in the traversal algorithm is NULL?

The algorithm exits and indicates the list is empty. (D) Signup and view all the answers

What is the main advantage of dynamic memory allocation?

It allows the size of a data structure to change during runtime. (B) Signup and view all the answers

Which of the following functions would you use to deallocate memory that was previously allocated?

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

What should be used when a program requires a continuous block of memory initialized to zero?

calloc() (C) Signup and view all the answers

In the context of circular linked lists, what is a characteristic of the last node?

It connects back to the first node. (C) Signup and view all the answers

Which of the following statements is incorrect regarding linked lists?

The last node in a circular linked list points to NULL. (B) Signup and view all the answers

What would happen if realloc() is used with a new size that is smaller than the originally allocated size?

The excess memory is automatically freed. (B) Signup and view all the answers

What distinguishes a doubly linked list from a singly linked list?

It contains two pointers, one for the previous and one for the next node. (C) Signup and view all the answers

In a circular linked list, where does the last node point?

It points to the first node. (A) Signup and view all the answers

What is the primary characteristic of a singly linked list?

It includes a pointer that points to the next node only. (B) Signup and view all the answers

What is the significance of the head pointer in a linked list?

It points to the first node of the list. (A) Signup and view all the answers

Which of the following structures is needed to represent a node in a doubly linked list?

struct node { int data; struct node *prev; struct node *next; } (B) Signup and view all the answers

In which type of linked list can traversal occur in either direction?

Doubly linked list (B) Signup and view all the answers

What happens to the last node in a singly linked list?

It points to NULL. (D) Signup and view all the answers

What type of linked list is described as having no starting and ending nodes?

Circular linked list (B) Signup and view all the answers

Which component is not found in a singly linked list node?

Previous pointer (A) Signup and view all the answers

What does the 'NULL' value represent in a linked list node?

The end of the list. (C) Signup and view all the answers

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Study Notes

Data Structure: Linked List

A linked list is a linear data structure made up of nodes, where each node contains data and a reference to the next node.
Easier insertion and deletion of elements compared to array-based data structures.
Commonly used as the underlying structure for stacks, queues, and associative arrays.
Nodes consist of a data field and a link or pointer to the next node.
The first node is termed the "head," while the last node can refer to the "tail" or link back to the head in circular lists.

Types of Linked Lists

Singly Linked List: Each node contains a data field and a single link to the next node.
Doubly Linked List: Nodes have two links; one points to the next node while the other points to the previous node, facilitating bidirectional traversal.
Circular Linked List: The last node's link points back to the first node, allowing continuous traversal without a null reference.
Doubly Circular Linked List: Similar to doubly linked lists but with circular connections at both ends.

Operations on Linked Lists

Traversing: Accessing each element only once; implemented using a pointer that moves through nodes using the link information.
Searching:
- Unsorted List: Sequentially access each node until the desired element is found, which can be time-consuming.
- Sorted List: Start from the head and compare until an element larger than the target is found, reducing the number of comparisons.
Inserting:
- At the beginning, using a pointer to update head and links accordingly.
- At a specific location, with checks for null conditions and memory availability.
- In a sorted list while maintaining the order.
Deleting:
- First Node: Simply update the head pointer and free the old node.
- Last Node: Traverse to the end node, update links, and free memory.
- Specific Node: Traverse, updating previous links to bypass the targeted node, deleting it afterward.

Node Structure Representation

Singly Linked List:

struct node {
    int data;
    struct node *next;
};

Doubly Linked List:

struct node {
    int data;
    struct node *next;
    struct node *prev;
};

Memory Management in C

Dynamic memory allocation is crucial for linked lists due to the need for flexible sizes.
Functions include:
- malloc(): Allocates uninitialized memory.
- calloc(): Allocates memory and initializes it to zero.
- free(): Deallocates previously allocated memory.
- realloc(): Changes the size of previously allocated memory blocks.

Key Characteristics

Linked lists do not have a fixed size, allowing dynamic resizing.
They can easily expand without memory wastage, a significant advantage over arrays.
Traversal in linked lists is inherently linear and can be inefficient for searches compared to other data structures like trees or hash tables.

Applications

Frequently utilized in applications where the number of elements is unknown or changes frequently, such as:
- Implementing data structures like stacks and queues.
- Managing resources in systems where elements need to be added and removed frequently.### Dynamic Memory Allocation in C
Dynamic memory allocation allows changing the size of a data structure, like an array, during runtime.
Essential when the number of required elements varies, such as reducing size from 9 to 5 or increasing from 9 to 12.
Achieved using four key C library functions defined in the <stdlib.h> header.

Functions for Dynamic Memory Allocation

malloc()
- Stands for "memory allocation."
- Allocates a single block of memory with a specified size.
- Does not initialize memory, leaving it with garbage values.
- Syntax: ptr = (cast-type*) malloc(byte-size);
- Example: ptr = (int*) malloc(100 * sizeof(int)); (allocates 400 bytes for 100 integers).
calloc()
- Stands for "contiguous allocation."
- Allocates multiple blocks of memory and initializes them with zero.
- Syntax: ptr = (cast-type*) calloc(n, element-size);
- Example: ptr = (float*) calloc(25, sizeof(float)); (allocates space for 25 floats).
free()
- Used to deallocate memory allocated by malloc() or calloc().
- Helps to prevent memory wastage by freeing unused memory.
- Syntax: free(ptr);
realloc()
- Re-allocates memory that has already been allocated.
- If current allocation is insufficient, realloc() changes size while preserving existing values.
- New blocks initialized with garbage values.
- Syntax: ptr = realloc(ptr, newSize);

Garbage Collection

Garbage Collection (GC) is a feature found in languages like C# and Java.
Automatically frees memory allocated to unused objects through garbage collectors (GC engines).
Prevents memory overflow and frees developers from manual memory management.
Reduces memory-related bugs like memory leaks and dangling pointers.
Languages without GC (like C and C++) require manual memory management, increasing potential for errors.
GC algorithms identify and remove unneeded objects, reclaiming memory without affecting used ones.

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