Basic concepts and nomenclatureEditEach record of a linked list is often called an 'element' or 'node'. Show
The field of each node that contains the address of the next node is usually called the 'next link' or 'next pointer'. The remaining fields are known as the 'data', 'information', 'value', 'cargo', or 'payload' fields. The 'head' of a list is its first node. The 'tail' of a list may refer either to the rest of the list after the head, or to the last node in the list. In Lisp and some derived languages, the next node may be called the 'cdr' (pronounced could-er) of the list, while the payload of the head node may be called the 'car'. Singly linked listEditSingly linked lists contain nodes which have a data field as well as 'next' field, which points to the next node in line of nodes. Operations that can be performed on singly linked lists include insertion, deletion and traversal. A singly linked list whose nodes contain two fields: an integer value and a link to the next node The following code demonstrates how to add a new node with data "value" to the end of a singly linked list: node addNode(node head, int value) {
node temp, p; // declare two nodes temp and p
temp = createNode(); // assume createNode creates a new node with data = 0 and next pointing to NULL.
temp->data = value; // add element's value to data part of node
if (head == NULL) {
head = temp; // when linked list is empty
}
else {
p = head; // assign head to p
while (p->next != NULL) {
p = p->next; // traverse the list until p is the last node. The last node always points to NULL.
}
p->next = temp; // Point the previous last node to the new node created.
}
return head;
}
Doubly linked listEditIn a 'doubly linked list', each node contains, besides the next-node link, a second link field pointing to the 'previous' node in the sequence. The two links may be called 'forward('s') and 'backwards', or 'next' and 'prev'('previous'). A doubly linked list whose nodes contain three fields: an integer value, the link forward to the next node, and the link backward to the previous node A technique known as XOR-linking allows a doubly linked list to be implemented using a single link field in each node. However, this technique requires the ability to do bit operations on addresses, and therefore may not be available in some high-level languages. Many modern operating systems use doubly linked lists to maintain references to active processes, threads, and other dynamic objects.[2] A common strategy for rootkits to evade detection is to unlink themselves from these lists.[3] Multiply linked listEditIn a 'multiply linked list', each node contains two or more link fields, each field being used to connect the same set of data records in a different order of same set (e.g., by name, by department, by date of birth, etc.). While doubly linked lists can be seen as special cases of multiply linked list, the fact that the two and more orders are opposite to each other leads to simpler and more efficient algorithms, so they are usually treated as a separate case. Circular linked listEditIn the last node of a list, the link field often contains a null reference, a special value is used to indicate the lack of further nodes. A less common convention is to make it point to the first node of the list; in that case, the list is said to be 'circular' or 'circularly linked'; otherwise, it is said to be 'open' or 'linear'. It is a list where the last pointer points to the first node. In the case of a circular doubly linked list, the first node also points to the last node of the list. Sentinel nodesEditIn some implementations an extra 'sentinel' or 'dummy' node may be added before the first data record or after the last one. This convention simplifies and accelerates some list-handling algorithms, by ensuring that all links can be safely dereferenced and that every list (even one that contains no data elements) always has a "first" and "last" node. Empty listsEditAn empty list is a list that contains no data records. This is usually the same as saying that it has zero nodes. If sentinel nodes are being used, the list is usually said to be empty when it has only sentinel nodes. Hash linkingEditThe link fields need not be physically part of the nodes. If the data records are stored in an array and referenced by their indices, the link field may be stored in a separate array with the same indices as the data records. List handlesEditSince a reference to the first node gives access to the whole list, that reference is often called the 'address', 'pointer', or 'handle' of the list. Algorithms that manipulate linked lists usually get such handles to the input lists and return the handles to the resulting lists. In fact, in the context of such algorithms, the word "list" often means "list handle". In some situations, however, it may be convenient to refer to a list by a handle that consists of two links, pointing to its first and last nodes. Combining alternativesEditThe alternatives listed above may be arbitrarily combined in almost every way, so one may have circular doubly linked lists without sentinels, circular singly linked lists with sentinels, etc. TradeoffsEditAs with most choices in computer programming and design, no method is well suited to all circumstances. A linked list data structure might work well in one case, but cause problems in another. This is a list of some of the common tradeoffs involving linked list structures. Linked lists vs. dynamic arraysEditA dynamic array is a data structure that allocates all elements contiguously in memory, and keeps a count of the current number of elements. 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 reallocate—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). This helps with appending elements at the array's end, but inserting into (or removing from) middle positions still carries prohibitive costs due to data moving to maintain contiguity. 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. This makes linked lists unsuitable for applications where it's useful to look up an element by its index quickly, such as heapsort. 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).[note 1] It can also be slow, and with a naïve allocator, wasteful, to allocate memory separately for each new element, a problem generally solved using memory pools. 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. linked lists is by implementing a program that resolves the Josephus problem. The Josephus problem is an election method that works by having a group of people stand in a circle. Starting at a predetermined person, one may count around the circle n times. Once the nth person is reached, one should remove them from the circle and have the members close the circle. The process is repeated until only one person is left. That person wins the election. This shows the strengths and weaknesses of a linked list vs. a dynamic array, because if the people are viewed as connected nodes in a circular linked list, then it shows how easily the linked list is able to delete nodes (as it only has to rearrange the links to the different nodes). 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. other listsEditWhile doubly linked and circular lists have advantages over singly linked linear lists, linear lists offer some advantages that make them preferable in some situations. 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 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 one—a simple example of a persistent data structure. Again, this is not true with the other variants: a node may never belong to two different circular or doubly linked lists. 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. Thus a Lisp procedure can safely take the CAR or CDR of any list. 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. Doubly linked vs. singly linkedEditDouble-linked lists require more space per node (unless one uses XOR-linking), and their elementary operations are more expensive; but they are often easier to manipulate because they allow fast and easy sequential access to the list in both directions. In a doubly linked list, one can insert or delete a node in a constant number of operations given only that node's address. 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. linearly linkedEditA circularly linked list may be a natural option to represent arrays that are naturally circular, e.g. the corners of a polygon, a pool of buffers that are used and released in FIFO ("first in, first out") order, or a set of processes that should be time-shared in round-robin order. 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.g., in the implementation of a queue), a circular structure allows one to handle the structure by a single pointer, instead of two. 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. For some applications, it can be useful to use singly linked lists that can vary between being circular and being linear, or even circular with a linear initial segment. Algorithms for searching or otherwise operating on these have to take precautions to avoid accidentally entering an endless loop. One usual method is to have a second pointer walking the list at half or double the speed, and if both pointers meet at the same node, you know you found a cycle. Using sentinel nodesEditSentinel 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. For example, when scanning the list looking for a node with a given value x, setting the sentinel's data field to x makes it unnecessary to test for end-of-list inside the loop. Another example is the merging two sorted lists: if their sentinels have data fields set to +∞, the choice of the next output node does not need special handling for empty 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.[8] Types of Linked ListA 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. In simple words, a linked list consists of nodes where each node contains a data field and a reference(link) to the next node in the list. Types Of Linked List
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1 2 3
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Created DLL is:
Traversal in forward direction
1 7 6
Traversal in reverse direction
6 7 1
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Contents of Circular Linked List
11 2 56 12
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Created circular doubly linked list is:
Traversal in forward direction
7 4 5
Traversal in reverse direction
5 4 7
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List After inserting 3 elements:
11 12 13
List After inserting 2 more elements:
11 12 13 14 15
Article Tags :
Data Structures Linked List
circular linked list doubly linked list Linked Lists Practice Tags :
Data Structures Linked List circular linked list Linked List MCQ : Operations on Linked List (Multiple Choice Questions)admin2013-06-02T03:31:15+00:00ITE6201 Data Structures and Algorithms(PreLim)Question1Answer saved Marked out of 1.00 Flag question Question textThe operation of processing each element in the list is known as ________________. Select one: a. inserting b. traversal c. merging d. sorting Clear my choice Question2Answer saved Marked out of 1.00 Flag question Question textThis form of access is used to add/remove nodes from a stack. Select one: a. None of these b. FIFO c. Both of these d. LIFO Clear my choice Question3Answer saved Marked out of 1.00 Flag question Question textIndexing the ________________ element in the list is not possible in linked lists. Select one: a. last b. middle c. first d. anywhere in between Clear my choice Question4Answer saved Marked out of 1.00 Flag question Question textThis indicates the end of the list. Select one: a. Last pointer b. Guard c. Sentinel d. End pointer Clear my choice Question5Answer saved Marked out of 1.00 Flag question Question textIn linked representation of stack, ___________ fields hold the elements of the stack. Select one: a. LINK b. INFO c. TOP d. NULL Clear my choice Question6Answer saved Marked out of 1.00 Flag question Question textStack follows the strategy of ________________. Select one: a. FIFO b. LIFO c. LRU d. RANDOM Clear my choice Question7Answer saved Marked out of 1.00 Flag question Question textIn the linked representation of the stack, __________ pointer behaves as the top pointer variable of stack. Select one: a. Begin b. Avail c. Start d. Stop Clear my choice Question8Answer saved Marked out of 1.00 Flag question Question textThis form of access is used to add and remove nodes from a queue. Select one: a. None of these b. LIFO, Last In First Out c. Both of these d. FIFO, First In First Out Clear my choice Question9Answer saved Marked out of 1.00 Flag question Question textLINK is the pointer pointing to the ____________________. Select one: a. predecessor node b. successor node c. head node d. last node Clear my choice Question10Answer saved Marked out of 1.00 Flag question Question textThis may take place only when there is some minimum amount or no space left in free storage list. Select one: a. Recycle bin b. Maintenance c. Memory management d. Garbage collection Clear my choice Question11Answer saved Marked out of 1.00 Flag question Question textEach node in a linked list must contain at least ___________________. Select one: a. Three fields b. Five fields c. Two fields d. Four fields Clear my choice Question12Answer saved Marked out of 1.00 Flag question Question textValue of first linked list index is _______________. Select one: a. -1 b. 0 c. 1 d. 2 Clear my choice Question13Answer saved Marked out of 1.00 Flag question Question textWhich is the pointer associated with the availability list? Select one: a. FIRST b. REAR c. TOP d. AVAIL Clear my choice Question14Answer saved Marked out of 1.00 Flag question Question textNew nodes are added to the ________ of the queue. Select one: a. Middle b. Front c. Back d. Front and Back Clear my choice Question15Answer saved Marked out of 1.00 Flag question Question textA linear list in which the pointer points only to the successive node. Select one: a. singly linked list b. circular linked list c. doubly linked list d. none of these Clear my choice Question16Answer saved Marked out of 1.00 Flag question Question textThe retrieval of items in a stack is ___________ operation. Select one: a. push b. retrieval c. access d. pop Clear my choice Question17Answer saved Marked out of 1.00 Flag question Question textThe situation when in a linked list START=NULL is ____________________. Select one: a. Overflow b. Houseful c. Underflow d. Saturated Clear my choice Question18Answer saved Marked out of 1.00 Flag question Question textThis is the term used to delete an element from the stack. Select one: a. Pull b. Pop c. Pump d. Push Clear my choice Question19Answer saved Marked out of 1.00 Flag question Question textEach node in singly linked list has _______ fields. Select one: a. 4 b. 1 c. 3 d. 2 Clear my choice Question20Answer saved Marked out of 1.00 Flag question Question textA linear list in which the last node points to the first node. Select one: a. none of these b. circular linked list c. singly linked list d. doubly linked list Clear my choice Question21Answer saved Marked out of 1.00 Flag question Question textLinked lists are best suited _____________________. Select one: a. for the size of the structure and the data in the structure are constantly changing b. data structure c. for relatively permanent collections of data d. for none of these situations Clear my choice Question22Answer saved Marked out of 1.00 Flag question Question textThe dummy header in linked list contains ____________________. Select one: a. first record of the actual data b. middle record of the actual data c. last record of the actual data d. pointer to the last record of the actual data Clear my choice Question23Answer saved Marked out of 1.00 Flag question Question textThe term used to insert an element into stack. Select one: a. pump b. pop c. pull d. push Clear my choice Question24Answer saved Marked out of 1.00 Flag question Question textIn linked representation of stack, the null pointer of the last node in the list signals _____________________. Select one: a. Bottom of the stack b. Middle of the stack c. In between some value d. Beginning of the stack Clear my choice Question25Answer saved Marked out of 1.00 Flag question Question textWhat is a run list? Select one: a. small batches of records from a file b. number of files in external storage c. number of elements having same value d. number of records Clear my choice Question26Answer saved Marked out of 1.00 Flag question Question textThe elements are removal from a stack in _________ order. Select one: a. Sequential b. Reverse c. Hierarchical d. Alternative Clear my choice Question27Answer saved Marked out of 1.00 Flag question Question textA pointer variable which contains the location at the top element of the stack. Select one: a. Top b. Final c. End d. Last Clear my choice Question28Answer saved Marked out of 1.00 Flag question Question textIn linked lists, there are no NULL links in ______________ Select one: a. single linked list b. linear doubly linked list c. linked list d. circular linked list Clear my choice Question29Answer saved Marked out of 1.00 Flag question Question textWhich is the pointer associated with the stack? Select one: a. FRONT b. FIRST c. TOP d. REAR Clear my choice Question30Answer saved Marked out of 1.00 Flag question Question textWhich of the following is an application of stack? Select one: a. infix to postfix b. all of these c. finding factorial d. tower of Hanoi Question1Answer saved Marked out of 1.00 Flag question Question textThis is the term used to delete an element from the stack. Select one: a. Pump b. Pull c. Push d. Pop Clear my choice Question2Answer saved Marked out of 1.00 Flag question Question textLinked lists are best suited _____________________. Select one: a. data structure b. for the size of the structure and the data in the structure are constantly changing c. for relatively permanent collections of data d. for none of these situations Clear my choice Question3Answer saved Marked out of 1.00 Flag question Question textStack follows the strategy of ________________. Select one: a. LIFO b. RANDOM c. LRU d. FIFO Clear my choice Question4Answer saved Marked out of 1.00 Flag question Question textA linear list in which the last node points to the first node. Select one: a. singly linked list b. none of these c. circular linked list d. doubly linked list Clear my choice Question5Answer saved Marked out of 1.00 Flag question Question textIn the linked representation of the stack, __________ pointer behaves as the top pointer variable of stack. Select one: a. Avail b. Start c. Stop d. Begin Clear my choice Question6Answer saved Marked out of 1.00 Flag question Question textThis is the insertion operation in the stack. Select one: a. pop b. top c. insert d. push Clear my choice Question7Answer saved Marked out of 1.00 Flag question Question textWhich of the following is an application of stack? Select one: a. finding factorial b. tower of Hanoi c. infix to postfix d. all of these Clear my choice Question8Answer saved Marked out of 1.00 Flag question Question textWhich of the following is two way lists? Select one: a. Linked list with header and trailer nodes b. List traversed in two directions c. Grounded header list d. Circular header list Clear my choice Question9Answer saved Marked out of 1.00 Flag question Question textEach node in a linked list must contain at least ___________________. Select one: a. Four fields b. Two fields c. Three fields d. Five fields Clear my choice Question10Answer saved Marked out of 1.00 Flag question Question textWhat is a queue? Select one: a. FILO b. LIFO c. LOFI d. FIFO Clear my choice Question11Answer saved Marked out of 1.00 Flag question Question textThis is a linear list in which insertions and deletions are made to form either end of the structure. Select one: a. Random of queue b. Circular queue c. Priority d. Dequeue Clear my choice Question12Answer saved Marked out of 1.00 Flag question Question textWhat happens when you push a new node onto a stack? Select one: a. The new node is placed at the back of the linked list b. The new node is placed at the front of the linked list c. No changes happen d. The new node is placed at the middle of the linked list Clear my choice Question13Answer saved Marked out of 1.00 Flag question Question textThe situation when in a linked list START=NULL is ____________________. Select one: a. Underflow b. Saturated c. Overflow d. Houseful Clear my choice Question14Answer saved Marked out of 1.00 Flag question Question textIn linked representation of stack, the null pointer of the last node in the list signals _____________________. Select one: a. Bottom of the stack b. Middle of the stack c. Beginning of the stack d. In between some value Clear my choice Question15Answer saved Marked out of 1.00 Flag question Question textThe elements are removal from a stack in _________ order. Select one: a. Alternative b. Hierarchical c. Reverse d. Sequential Clear my choice Question16Answer saved Marked out of 1.00 Flag question Question textThe term used to insert an element into stack. Select one: a. pop b. pull c. pump d. push Clear my choice Question17Answer saved Marked out of 1.00 Flag question Question textValue of first linked list index is _______________. Select one: a. 2 b. 0 c. -1 d. 1 Clear my choice Question18Answer saved Marked out of 1.00 Flag question Question textA linear list in which the pointer points only to the successive node. Select one: a. circular linked list b. singly linked list c. none of these d. doubly linked list Clear my choice Question19Answer saved Marked out of 1.00 Flag question Question textThe termpushandpopis related to _____________. Select one: a. lists b. trees c. stacks d. array Clear my choice Question20Answer saved Marked out of 1.00 Flag question Question textIn a linked list, the ____________ contains the address of next element in the list. Select one: a. Start field b. Next element field c. Link field d. Info field Clear my choice Question21Answer saved Marked out of 1.00 Flag question Question textThe dummy header in linked list contains ____________________. Select one: a. first record of the actual data b. last record of the actual data c. middle record of the actual data d. pointer to the last record of the actual data Clear my choice Question22Answer saved Marked out of 1.00 Flag question Question textWhich of the following names does not relate to stacks? Select one: a. FIFO lists b. LIFO lists c. Piles d. Push down lists Clear my choice Question23Answer saved Marked out of 1.00 Flag question Question textThe retrieval of items in a stack is ___________ operation. Select one: a. push b. retrieval c. access d. pop Clear my choice Question24Answer saved Marked out of 1.00 Flag question Question textWhich is the pointer associated with the availability list? Select one: a. TOP b. AVAIL c. REAR d. FIRST Clear my choice Question25Answer saved Marked out of 1.00 Flag question Question textWhich is the pointer associated with the stack? Select one: a. TOP b. FIRST c. FRONT d. REAR Clear my choice Question26Answer saved Marked out of 1.00 Flag question Question textThe operation of processing each element in the list is known as ________________. Select one: a. merging b. inserting c. traversal d. sorting Clear my choice Question27Answer saved Marked out of 1.00 Flag question Question textIn linked lists, there are no NULL links in ______________ Select one: a. single linked list b. circular linked list c. linked list d. linear doubly linked list Clear my choice Question28Answer saved Marked out of 1.00 Flag question Question textNew nodes are added to the ________ of the queue. Select one: a. Front and Back b. Middle c. Front d. Back Clear my choice Question29Answer saved Marked out of 1.00 Flag question Question textThis form of access is used to add and remove nodes from a queue. Select one: a. None of these b. LIFO, Last In First Out c. FIFO, First In First Out d. Both of these Clear my choice Question30Answer saved Marked out of 1.00 Flag question Question textEach node in singly linked list has _______ fields. Select one: a. 1 b. 3 c. 2 d. 4 Types of Linked List and Operation on Linked ListIn the previous blog, we have seen the structure and properties of a Linked List. In this blog, we will discuss the types of a linked list and basic operations that can be performed on a linked list. Types of Linked ListFollowing are the types of linked list
Singly Linked ListA Singly-linked list is a collection of nodes linked together in a sequential way where each node of the singly linked list contains a data field and an address field that contains the reference of the next node. The structure of the node in the Singly Linked List is class Node {
int data // variable to store the data of the node
Node next // variable to store the address of the next node
} The nodes are connected to each other in this form where the value of the next variable of the last node is NULL i.e. next = NULL, which indicates the end of the linked list. Doubly Linked ListA Doubly Linked List contains an extra memory to store the address of the previous node, together with the address of the next node and data which are there in the singly linked list. So, here we are storing the address of the next as well as the previous nodes. The following is the structure of the node in the Doubly Linked List(DLL): class DLLNode {
int val // variable to store the data of the node
DLLNode prev // variable to store the address of the previous node
DLLNode next // variable to store the address of the next node
} The nodes are connected to each other in this form where the first node has prev = NULL and the last node has next = NULL. Advantages over Singly Linked List-
Disadvantages over Singly Linked List-
Circular Linked ListA circular linked list is either a singly or doubly linked list in which there are no NULL values. Here, we can implement the Circular Linked List by making the use of Singly or Doubly Linked List. In the case of a singly linked list, the next of the last node contains the address of the first node and in case of a doubly-linked list, the next of last node contains the address of the first node and prev of the first node contains the address of the last node. Advantages of a Circular linked list
Disadvantages of Circular linked list
Basic Operations on Linked List
We will see the various implementation of these operations on a singly linked list. Following is the structure of the node in a linked list: class Node{ int data // variable containing the data of the node Node next // variable containing the address of next node }Linked List TraversalThe idea here is to step through the list from beginning to end. For example, we may want to print the list or search for a specific node in the list. The algorithm for traversing a list
Linked List node InsertionThere can be three cases that will occur when we are inserting a node in a linked list.
Insertion at the beginning Since there is no need to find the end of the list. If the list is empty, we make the new node as the head of the list. Otherwise, we we have to connect the new node to the current head of the list and make the new node, the head of the list. // function is returning the head of the singly linked-list
Node insertAtBegin(Node head, int val)
{
newNode = new Node(val) // creating new node of linked list
if(head == NULL) // check if linked list is empty
return newNode
else // inserting the node at the beginning
{
newNode.next = head
return newNode
}
} Insertion at end We will traverse the list until we find the last node. Then we insert the new node to the end of the list. Note that we have to consider special cases such as list being empty. In case of a list being empty, we will return the updated head of the linked list because in this case, the inserted node is the first as well as the last node of the linked list. // the function is returning the head of the singly linked list
Node insertAtEnd(Node head, int val)
{
if( head == NULL ) // handing the special case
{
newNode = new Node(val)
head = newNode
return head
}
Node temp = head
// traversing the list to get the last node
while( temp.next != NULL )
{
temp = temp.next
}
newNode = new Node(val)
temp.next = newNode
return head
} Insertion after a given node We are given the reference to a node, and the new node is inserted after the given node. void insertAfter(Node prevNode, int val)
{
newNode = new Node(val)
newNode.next = prevNode.next
prevNode.next = newNode
} NOTE: If the address of the prevNode is not given, then you can traverse to that node by finding the data value. Linked List node DeletionTo delete a node from a linked list, we need to do these steps
In the deletion, there is a special case in which the first node is deleted. In this, we need to update the head of the linked list. // this function will return the head of the linked list
Node deleteLL(Node head, Node del)
{
if(head == del) // if the node to be deleted is the head node
{
return head.next // special case for the first Node
}
Node temp = head
while( temp.next != NULL )
{
if(temp.next == del) // finding the node to be deleted
{
temp.next = temp.next.next
delete del // free the memory of that Node
return head
}
temp = temp.next
}
return head // if no node matches in the Linked List
} Linked List node SearchingTo search any value in the linked list, we can traverse the linked list and compares the value present in the node. bool searchLL(Node head, int val) { Node temp = head // creating a temp variable pointing to the head of the linked list while( temp != NULL) // traversing the list { if( temp.data == val ) return true temp = temp.next } return false }Linked List node UpdationTo update the value of the node, we just need to set the data part to the new value. Below is the implementation in which we had to update the value of the first node in which data is equal to val and we have to set it to newVal. void updateLL(Node head, int val, int newVal) { Node temp = head while(temp != NULL) { if( temp.data == val) { temp.data = newVal return } temp = temp.next } }Suggested Problems to solve in Linked List
Happy coding! Enjoy Algorithms. |