Chapter 1 : What is an application of linear linked list data structures? - Quora A linked list is a linear data structure, in which the elements are not stored at contiguous memory locations. The elements in a linked list are linked using pointers as shown in the below image: In simple words, a linked list consists of nodes where each node contains a data field and a reference. If the space reserved for the dynamic array is exceeded, it is reallocated and possibly copied, which is an expensive operation. Linked lists have several advantages over dynamic arrays. Insertion or deletion of an element at a specific point of a list, assuming that we have indexed a pointer to the node before the one to be removed, or before the insertion point already, is a constant-time operation otherwise without this reference it is O n, whereas insertion in a dynamic array at random locations will require moving half of the elements on average, and all the elements in the worst case. While one can "delete" an element from an array in constant time by somehow marking its slot as "vacant", this causes fragmentation that impedes the performance of iteration. Moreover, arbitrarily many elements may be inserted into a linked list, limited only by the total memory available; while a dynamic array will eventually fill up its underlying array data structure and will have to reallocateâ an expensive operation, one that may not even be possible if memory is fragmented, although the cost of reallocation can be averaged over insertions, and the cost of an insertion due to reallocation would still be amortized O 1. An array from which many elements are removed may also have to be resized in order to avoid wasting too much space. On the other hand, dynamic arrays as well as fixed-size array data structures allow constant-time random access, while linked lists allow only sequential access to elements. Singly linked lists, in fact, can be easily traversed in only one direction. Sequential access on arrays and dynamic arrays is also faster than on linked lists on many machines, because they have optimal locality of reference and thus make good use of data caching. Another disadvantage of linked lists is the extra storage needed for references, which often makes them impractical for lists of small data items such as characters or boolean values, because the storage overhead for the links may exceed by a factor of two or more the size of the data. In contrast, a dynamic array requires only the space for the data itself and a very small amount of control data. Some hybrid solutions try to combine the advantages of the two representations. Unrolled linked lists store several elements in each list node, increasing cache performance while decreasing memory overhead for references. CDR coding does both these as well, by replacing references with the actual data referenced, which extends off the end of the referencing record. A good example that highlights the pros and cons of using dynamic arrays vs. The Josephus problem is an election method that works by having a group of people stand in a circle. Starting at a predetermined person, you count around the circle n times. Once you reach the nth person, take them out of the circle and have the members close the circle. Then count around the circle the same n times and repeat the process, until only one person is left. That person wins the election. This shows the strengths and weaknesses of a linked list vs. However, the linked list will be poor at finding the next person to remove and will need to search through the list until it finds that person. A dynamic array, on the other hand, will be poor at deleting nodes or elements as it cannot remove one node without individually shifting all the elements up the list by one. However, it is exceptionally easy to find the nth person in the circle by directly referencing them by their position in the array. The list ranking problem concerns the efficient conversion of a linked list representation into an array. Although trivial for a conventional computer, solving this problem by a parallel algorithm is complicated and has been the subject of much research. A balanced tree has similar memory access patterns and space overhead to a linked list while permitting much more efficient indexing, taking O log n time instead of O n for a random access. However, insertion and deletion operations are more expensive due to the overhead of tree manipulations to maintain balance. Schemes exist for trees to automatically maintain themselves in a balanced state: AVL trees or red-black trees. Singly linked linear lists vs. A singly linked linear list is a recursive data structure, because it contains a pointer to a smaller object of the same type. For that reason, many operations on singly linked linear lists such as merging two lists, or enumerating the elements in reverse order often have very simple recursive algorithms, much simpler than any solution using iterative commands. While those recursive solutions can be adapted for doubly linked and Page 1
circularly linked lists, the procedures generally need extra arguments and more complicated base cases. Linear singly linked lists also allow tail-sharing, the use of a common final portion of sub-list as the terminal portion of two different lists. In particular, if a new node is added at the beginning of a list, the former list remains available as the tail of the new oneâ a simple example of a persistent data structure. Again, this is not true with the other variants: In particular, end-sentinel nodes can be shared among singly linked non-circular lists. The same end-sentinel node may be used for every such list. In Lisp, for example, every proper list ends with a link to a special node, denoted by nil or, whose CAR and CDR links point to itself. The advantages of the fancy variants are often limited to the complexity of the algorithms, not in their efficiency. A circular list, in particular, can usually be emulated by a linear list together with two variables that point to the first and last nodes, at no extra cost. To do the same in a singly linked list, one must have the address of the pointer to that node, which is either the handle for the whole list in case of the first node or the link field in the previous node. Some algorithms require access in both directions. On the other hand, doubly linked lists do not allow tail-sharing and cannot be used as persistent data structures Circularly linked vs. In these applications, a pointer to any node serves as a handle to the whole list. With a circular list, a pointer to the last node gives easy access also to the first node, by following one link. Thus, in applications that require access to both ends of the list e. A circular list can be split into two circular lists, in constant time, by giving the addresses of the last node of each piece. The operation consists in swapping the contents of the link fields of those two nodes. Applying the same operation to any two nodes in two distinct lists joins the two list into one. This property greatly simplifies some algorithms and data structures, such as the quad-edge and face-edge. The simplest representation for an empty circular list when such a thing makes sense is a null pointer, indicating that the list has no nodes. Without this choice, many algorithms have to test for this special case, and handle it separately. By contrast, the use of null to denote an empty linear list is more natural and often creates fewer special cases. Using sentinel nodes[ edit ] Sentinel node may simplify certain list operations, by ensuring that the next or previous nodes exist for every element, and that even empty lists have at least one node. One may also use a sentinel node at the end of the list, with an appropriate data field, to eliminate some end-of-list tests. Another example is the merging two sorted lists: However, sentinel nodes use up extra space especially in applications that use many short lists, and they may complicate other operations such as the creation of a new empty list. However, if the circular list is used merely to simulate a linear list, one may avoid some of this complexity by adding a single sentinel node to every list, between the last and the first data nodes. With this convention, an empty list consists of the sentinel node alone, pointing to itself via the next-node link. The list handle should then be a pointer to the last data node, before the sentinel, if the list is not empty; or to the sentinel itself, if the list is empty. The same trick can be used to simplify the handling of a doubly linked linear list, by turning it into a circular doubly linked list with a single sentinel node. However, in this case, the handle should be a single pointer to the dummy node itself. This makes algorithms for inserting or deleting linked list nodes somewhat subtle. This section gives pseudocode for adding or removing nodes from singly, doubly, and circularly linked lists in-place. Throughout we will use null to refer to an end-of-list marker or sentinel, which may be implemented in a number of ways. Linearly linked lists[ edit ] Singly linked lists[ edit ] Our node data structure will have two fields. We also keep a variable firstnode which always points to the first node in the list, or is null for an empty list. The diagram shows how it works. Inserting a node before an existing one cannot be done directly; instead, one must keep track of the previous node and insert a node after it. This requires updating firstnode. The diagram demonstrates the former. To find and remove a particular node, one must again keep track of the previous element. Inserting to a list before a specific node requires traversing the list, which would have a worst case running time of O n. Appending one linked list to another can be inefficient unless a reference to the tail is kept as part of the List structure, because we must traverse the entire first list in order to find the tail, and then append the second list to this. Thus, if two linearly linked lists are each of length n, list appending has asymptotic time complexity of O. Page 2
Chapter 2 : Linked List Program in C Singly linked list is the most basic linked data structure. In this the elements can be placed anywhere in the heap memory unlike array which uses contiguous locations. Simplest programming tutorials for beginners What do you want to learn today? Linked List In this tutorial, you will learn about linked list and its applications. You will also learn how to create and perform different operations on a linked list. In a game of Treasure Hunt, you start by looking for the first clue. When you find it, instead of having the treasure, it has the location of the next clue and so on. You keep following the clues until you get to the treasure. A linked list is similar. It is a series of connected "nodes" that contains the "address" of the next node. Each node can store a data point which may be a number, a string or any other type of data. Also, the last node in the linkedlist can be identified because its next portion points to NULL. How another node is referenced? Some pointer magic is involved. A data item An address of another node We wrap both the data item and the next node reference in a struct as: Each struct node has a data item and a pointer to another struct node. Let us create a simple Linked List with three items to understand how this works. In just a few steps, we have created a simple linkedlist with three nodes. The power of linkedlist comes from the ability to break the chain and rejoin it. Create a new struct node and allocate memory to it. Add its data value as 4 Point its next pointer to the struct node containing 2 as data value Change next pointer of "1" to the node we just created. Doing something similar in an array would have required shifting the positions of all the subsequent elements. Apart from that, linked lists are a great way to learn how pointers work. By practicing how to manipulate linked lists, you can prepare yourself to learn more advanced data structures like graphs and trees. Page 3
Chapter 3 : Linked List Data Structure Interview Cake A linked list is a way to store a collection of elements. Like an array these can be character or integers. Each element in a linked list is stored in the form of a node. By Muhammad Asif - February 08, Linked list is a linear data structure. It is a list or chain of nodes where each node stores data as well as points to the next node and previous node also for double linked list in the list. It means that each node contains the data and also the location of the next node. Thus each node of the list is linked logically with the next node through a linkpointer. The head of a linked list is its first node. The tail of a linked list refers to the last node in the list. Last node has a Null reference. A node may contain data of any type. However, all nodes of the list contain the same type data. A simple linked list is shown in the following image. Each node of the linked list has two parts: It stores the actual data. It can consist of one or more fields. These fields are known as data, information, value, cargo, or payload fields. It stores the memory address of the next node. It is usually, known as next link or next pointer. If there is no next node, then a null value is stored in it, to mark the end of the list. In the above image, nodes of the linked list contain two fields: The last node is linked to a terminator that indicates the end of the list. There are two types of linked lists: Sometimes, it is also simply called single linked list It does not contain the address of the previous node. It can be accessed or visited from beginning to its end such as only in one direction. The singly linked list is also known as one-way list or one-way chain. In singly linked list, each node consists of at least two fields. The first field contains the data. This field is called data field more than one data fields can be used in a node to store information. The second field contains the pointer or link to the next node in the list. This field is called next link or next painter field. The next link field of the last node contains a NULL value. The singly linked list that has no node is called empty list. It has a value NULL. Following diagram shows singly linked list with two data fields and one next pointer field. A linked list is accessed with the reference to the address of its first node. Suppose memory address of the first node is The second node is created and its memory address is stored in the next-pointer member of first node. Suppose its memory address is In the above diagram, and represent the memory addresses of third node and fourth node respectively. The last node of the list contains a NULL value in its next-pointer field. Representation of Singly Linked List The storage technique of linked list is different than linear array. The elements or items of a linked list are stored in memory in scattered form but these are linked together through pointers. Each element or item of the linked list is called an object. One object may contain one or more fields. Each node of linked list contains at least two fields. One field is used to store data and the other to store address of memory location of the next object. In this way, the nodes of list are linked together in the form of a chain. The "link" is defined as a pointer to the object "student" which will be used as next-pointer. It is used to store the memory address. It contains the memory address of the next node in the chain. This operator allocates memory for the specified object and returns its memory address to the pointer variable. Its general syntax is as follows: It may be the name of a defined class or structure. Following statements declares a pointer variable "start" to an object "student" and creates a node of "student". It is used to store the memory address of the first or starting object in the singly linked list. The storage memory will be as following image: While creating a new node, the address of the previous node is stored in a pointer variable. The memory address of newly created item is stored in the pointer field of the previous node. The representation of singly linked list having nodes in memory is shown in the following image: The above list is a linear linked list. It does not occupy consecutive memory locations like an array. Each element or item of the list is at a different location. These are at memory addresses,, and Each node has a pointer variable that holds the address of next node. The pointer of the last node does not point to any node. It contains NULL value. The whole list is accessed with reference of the pointer object that holds the starting address of the linked list. Deleting Node The memory allocated through "new" operator will be reserved for a node until the program is terminated. This may create many problems if the size of program is very large. We can de-allocate the memory allocated with "new" operator and it can be re-allocated for other parts of current program or operating system. The "delete" operator is used to de-allocate memory occupied by a node. The general syntax Page 4
of "delete" operator is given below: Linked List Example Programs Example program 1: The following program creates a linked list having 5 real values and finds largest and smallest values from list. Enter 5 real values. Page 5
Chapter 4 : Linked list in C Programming Simplified A linked list is a sequence of data structures, which are connected together via links. Linked List is a sequence of links which contains items. Each link contains a connection to another link. Linked list is the second most-used data structure after array. Data Structure and Algorithms - Linked List Advertisements Next Page A linked list is a sequence of data structures, which are connected together via links. Linked List is a sequence of links which contains items. Each link contains a connection to another link. Linked list is the second most-used data structure after array. Following are the important terms to understand the concept of Linked List. Linked List Representation Linked list can be visualized as a chain of nodes, where every node points to the next node. As per the above illustration, following are the important points to be considered. Linked List contains a link element called first. Each link carries a data field s and a link field called next. Each link is linked with its next link using its next link. Last link carries a link as null to mark the end of the list. Types of Linked List Following are the various types of linked list. Basic Operations Following are the basic operations supported by a list. Insertion Operation Adding a new node in linked list is a more than one step activity. We shall learn this with diagrams here. First, create a node using the same structure and find the location where it has to be inserted. While inserting it at the end, the second last node of the list should point to the new node and the new node will point to NULL. Deletion Operation Deletion is also a more than one step process. We shall learn with pictorial representation. First, locate the target node to be removed, by using searching algorithms. Now, using the following code, we will remove what the target node is pointing at. We can keep that in memory otherwise we can simply deallocate memory and wipe off the target node completely. Reverse Operation This operation is a thorough one. We need to make the last node to be pointed by the head node and reverse the whole linked list. First, we traverse to the end of the list. It should be pointing to NULL. Now, we shall make all left side nodes point to their previous nodes one by one. Except the node first node pointed by the head node, all nodes should point to their predecessor, making them their new successor. The first node will point to NULL. The linked list is now reversed. To see linked list implementation in C programming language, please click here. Chapter 5 : C++ : Linked lists in C++ (Singly linked list) Linked list is one of the most important data structures. We often face situations, where the data is dynamic in nature and number of data can't be predicted or the number of data keeps changing during program execution. Chapter 6 : C Program to Create Singly Linked List.using Node Structure - Data Structure - theinnatdunvill The C programs in this section provides various implementations of other data structures using linked list. It has programs to implement a Stack, to implement a Queue, to implement a Doubly Linked List, a Circular Doubly Linked List and a Binary Tree using linked list. Chapter 7 : Linked list - Wikipedia Linked list is one of the fundamental data structures in C. Knowledge of linked lists is must for C programmers. This article explains the fundamentals of C linked list with an example C program. Linked list is a dynamic data structure whose length can be increased or decreased at run time. How. Chapter 8 : C++ Linked List Data Structure (with examples) - CodeHim Enter the data: 10 Do you want to creat another: y Enter the data: 20 Do you want to creat another: y Enter the data: 30 Do you want to creat another: n The Linked List: >>>NULL. Page 6
Chapter 9 : Singly Linked List Tutorials & Notes Data Structures HackerEarth Linked list is a type of data structure provided in C language to make use of pointer efficiently. Introduction to Linked List It is a data Structure which consists if group of nodes that forms a sequence. Page 7