Condiție prealabilă: Ca și matricele, Linked List este o structură de date liniară. Spre deosebire de matrice, elementele listei legate nu sunt stocate în locația adiacentă, elementele sunt legate folosind pointeri așa cum se arată mai jos.

Ca și matricele, Linked List este o structură de date liniară. Spre deosebire de matrice, elementele listei legate nu sunt stocate în locația adiacentă, elementele sunt legate folosind pointeri așa cum se arată mai jos.

În Java, LinkedList poate fi reprezentat ca o clasă și un Node ca o clasă separată. Clasa LinkedList conține o referință de tipul clasei Node.

Java

class> LinkedList {> > Node head;> // head of list> > /* Linked list Node*/> > static> class> Node {> > int> data;> > Node next;> > // Constructor to create a new node> > // Next is by default initialized> > // as null> > Node(> int> d) { data = d; }> > }> }>

Creare și inserare:

În acest articol, inserarea în listă se face la sfârșit, adică noul nod este adăugat după ultimul nod al listei legate date. De exemplu, dacă lista legată dată este 5->10->15->20->25 și trebuie inserat 30, atunci lista legată devine 5->10->15->20->25->30 .
Deoarece o listă legată este de obicei reprezentată de indicatorul de cap al acesteia, este necesar să parcurgeți lista până la ultimul nod și apoi să schimbați până la ultimul nod în noul nod.

Implementare:

Java

import> java.io.*;> > // Java program to implement> // a Singly Linked List> public> class> LinkedList {> > > Node head;> // head of list> > > // Linked list Node.> > // This inner class is made static> > // so that main() can access it> > static> class> Node {> > > int> data;> > Node next;> > > // Constructor> > Node(> int> d)> > {> > data = d;> > next => null> ;> > }> > }> > > // Method to insert a new node> > public> static> LinkedList insert(LinkedList list,> int> data)> > {> > // Create a new node with given data> > Node new_node => new> Node(data);> > > > // If the Linked List is empty,> > // then make the new node as head> > if> (list.head ==> null> ) {> > list.head = new_node;> > }> > else> {> > // Else traverse till the last node> > // and insert the new_node there> > Node last = list.head;> > while> (last.next !=> null> ) {> > last = last.next;> > }> > > // Insert the new_node at last node> > last.next = new_node;> > }> > > // Return the list by head> > return> list;> > }> > > // Method to print the LinkedList.> > public> static> void> printList(LinkedList list)> > {> > Node currNode = list.head;> > > System.out.print(> 'LinkedList: '> );> > > // Traverse through the LinkedList> > while> (currNode !=> null> ) {> > // Print the data at current node> > System.out.print(currNode.data +> ' '> );> > > // Go to next node> > currNode = currNode.next;> > }> > }> > > // Driver code> > public> static> void> main(String[] args)> > {> > /* Start with the empty list. */> > LinkedList list => new> LinkedList();> > > //> > // ******INSERTION******> > //> > > // Insert the values> > list = insert(list,> 1> );> > list = insert(list,> 2> );> > list = insert(list,> 3> );> > list = insert(list,> 4> );> > list = insert(list,> 5> );> > list = insert(list,> 6> );> > list = insert(list,> 7> );> > list = insert(list,> 8> );> > > // Print the LinkedList> > printList(list);> > }> }>

Ieșire

LinkedList: 1 2 3 4 5 6 7 8 

Traversare: Pentru traversare, mai jos este o funcție de uz general printList() care tipărește orice listă dată prin parcurgerea listei de la nodul principal la ultimul.

Implementare:

Java

import> java.io.*;> // Java program to implement> // a Singly Linked List> public> class> LinkedList {> > Node head;> // head of list> > // Linked list Node.> > // Node is a static nested class> > // so main() can access it> > static> class> Node {> > int> data;> > Node next;> > // Constructor> > Node(> int> d)> > {> > data = d;> > next => null> ;> > }> > }> > // Method to insert a new node> > public> static> LinkedList insert(LinkedList list,> > int> data)> > {> > // Create a new node with given data> > Node new_node => new> Node(data);> > new_node.next => null> ;> > // If the Linked List is empty,> > // then make the new node as head> > if> (list.head ==> null> ) {> > list.head = new_node;> > }> > else> {> > // Else traverse till the last node> > // and insert the new_node there> > Node last = list.head;> > while> (last.next !=> null> ) {> > last = last.next;> > }> > // Insert the new_node at last node> > last.next = new_node;> > }> > // Return the list by head> > return> list;> > }> > // Method to print the LinkedList.> > public> static> void> printList(LinkedList list)> > {> > Node currNode = list.head;> > System.out.print(> 'LinkedList: '> );> > // Traverse through the LinkedList> > while> (currNode !=> null> ) {> > // Print the data at current node> > System.out.print(currNode.data +> ' '> );> > // Go to next node> > currNode = currNode.next;> > }> > }> > // **************MAIN METHOD**************> > // method to create a Singly linked list with n nodes> > public> static> void> main(String[] args)> > {> > /* Start with the empty list. */> > LinkedList list => new> LinkedList();> > //> > // ******INSERTION******> > //> > // Insert the values> > list = insert(list,> 1> );> > list = insert(list,> 2> );> > list = insert(list,> 3> );> > list = insert(list,> 4> );> > list = insert(list,> 5> );> > list = insert(list,> 6> );> > list = insert(list,> 7> );> > list = insert(list,> 8> );> > // Print the LinkedList> > printList(list);> > }> }>

Ieșire

LinkedList: 1 2 3 4 5 6 7 8 

Ștergere prin CHEIE:

Procesul de ștergere poate fi înțeles după cum urmează:

Să fie făcut:

Având o „cheie”, ștergeți prima apariție a acestei chei din lista legată .

Cum să o facă:

Pentru a șterge un nod din lista legată, urmați pașii următori.

1. Căutați cheia pentru prima sa apariție în listă
2. Acum, oricare dintre cele 3 condiții poate fi acolo:
   • Cazul 1: Cheia se găsește la cap
     1. În acest caz, Schimbați capul nodului la următorul nod al capului curent.
        
     2. Eliberați memoria nodului principal înlocuit.
   • Cazul 2: Cheia se găsește la mijloc sau ultima, cu excepția cap
     1. În acest caz, Găsiți nodul anterior al nodului de șters.
     2. Schimbați următorul nod anterior cu următorul nod al nodului curent.
     3. Eliberați memoria nodului înlocuit.
   • Cazul 3: Cheia nu este găsită în listă
     1. În acest caz, nu trebuie efectuată nicio operațiune.

Implementare:

Java

import> java.io.*;> // Java program to implement> // a Singly Linked List> public> class> LinkedList {> > Node head;> // head of list> > // Linked list Node.> > // Node is a static nested class> > // so main() can access it> > static> class> Node {> > int> data;> > Node next;> > // Constructor> > Node(> int> d)> > {> > data = d;> > next => null> ;> > }> > }> > // Method to insert a new node> > public> static> LinkedList insert(LinkedList list,> > int> data)> > {> > // Create a new node with given data> > Node new_node => new> Node(data);> > new_node.next => null> ;> > // If the Linked List is empty,> > // then make the new node as head> > if> (list.head ==> null> ) {> > list.head = new_node;> > }> > else> {> > // Else traverse till the last node> > // and insert the new_node there> > Node last = list.head;> > while> (last.next !=> null> ) {> > last = last.next;> > }> > // Insert the new_node at last node> > last.next = new_node;> > }> > // Return the list by head> > return> list;> > }> > // Method to print the LinkedList.> > public> static> void> printList(LinkedList list)> > {> > Node currNode = list.head;> > System.out.print(> 'LinkedList: '> );> > // Traverse through the LinkedList> > while> (currNode !=> null> ) {> > // Print the data at current node> > System.out.print(currNode.data +> ' '> );> > // Go to next node> > currNode = currNode.next;> > }> > System.out.println();> > }> > // **************DELETION BY KEY**************> > // Method to delete a node in the LinkedList by KEY> > public> static> LinkedList deleteByKey(LinkedList list,> > int> key)> > {> > // Store head node> > Node currNode = list.head, prev => null> ;> > //> > // CASE 1:> > // If head node itself holds the key to be deleted> > if> (currNode !=> null> && currNode.data == key) {> > list.head = currNode.next;> // Changed head> > // Display the message> > System.out.println(key +> ' found and deleted'> );> > // Return the updated List> > return> list;> > }> > //> > // CASE 2:> > // If the key is somewhere other than at head> > //> > // Search for the key to be deleted,> > // keep track of the previous node> > // as it is needed to change currNode.next> > while> (currNode !=> null> && currNode.data != key) {> > // If currNode does not hold key> > // continue to next node> > prev = currNode;> > currNode = currNode.next;> > }> > // If the key was present, it should be at currNode> > // Therefore the currNode shall not be null> > if> (currNode !=> null> ) {> > // Since the key is at currNode> > // Unlink currNode from linked list> > prev.next = currNode.next;> > // Display the message> > System.out.println(key +> ' found and deleted'> );> > }> > //> > // CASE 3: The key is not present> > //> > // If key was not present in linked list> > // currNode should be null> > if> (currNode ==> null> ) {> > // Display the message> > System.out.println(key +> ' not found'> );> > }> > // return the List> > return> list;> > }> > // **************MAIN METHOD**************> > // method to create a Singly linked list with n nodes> > public> static> void> main(String[] args)> > {> > /* Start with the empty list. */> > LinkedList list => new> LinkedList();> > //> > // ******INSERTION******> > //> > // Insert the values> > list = insert(list,> 1> );> > list = insert(list,> 2> );> > list = insert(list,> 3> );> > list = insert(list,> 4> );> > list = insert(list,> 5> );> > list = insert(list,> 6> );> > list = insert(list,> 7> );> > list = insert(list,> 8> );> > // Print the LinkedList> > printList(list);> > //> > // ******DELETION BY KEY******> > //> > // Delete node with value 1> > // In this case the key is ***at head***> > deleteByKey(list,> 1> );> > // Print the LinkedList> > printList(list);> > // Delete node with value 4> > // In this case the key is present ***in the> > // middle***> > deleteByKey(list,> 4> );> > // Print the LinkedList> > printList(list);> > // Delete node with value 10> > // In this case the key is ***not present***> > deleteByKey(list,> 10> );> > // Print the LinkedList> > printList(list);> > }> }>

Ieșire

LinkedList: 1 2 3 4 5 6 7 8 1 found and deleted LinkedList: 2 3 4 5 6 7 8 4 found and deleted LinkedList: 2 3 5 6 7 8 10 not found LinkedList: 2 3 5 6 7 8 

Ștergere la poziție:

Acest proces de ștergere poate fi înțeles după cum urmează:

Să fie făcut:
Având în vedere a 'poziţie' , ștergeți nodul din această poziție din lista legată .
Cum să o facă:

Pașii pentru a face acest lucru sunt următorii:

1. Parcurgeți lista numărând indexul nodurilor
2. Pentru fiecare index, potriviți indicele să fie același cu poziția
3. Acum, oricare dintre cele 3 condiții poate fi acolo:
   • Cazul 1: Poziția este 0, adică capul trebuie șters
     1. În acest caz, Schimbați capul nodului la următorul nod al capului curent.
        
     2. Eliberați memoria nodului principal înlocuit.
   • Cazul 2: Poziția este mai mare decât 0, dar mai mică decât dimensiunea listei, adică la mijloc sau ultimul, cu excepția capului
     1. În acest caz, Găsiți nodul anterior al nodului de șters.
        
     2. Schimbați următorul nod anterior cu următorul nod al nodului curent.
     3. Eliberați memoria nodului înlocuit.
   • Cazul 3: poziția este mai mare decât dimensiunea listei, adică poziția nu a fost găsită în listă
     1. În acest caz, nu trebuie efectuată nicio operațiune.

Implementare:

Java

import> java.io.*;> // Java program to implement> // a Singly Linked List> public> class> LinkedList {> > Node head;> // head of list> > // Linked list Node.> > // Node is a static nested class> > // so main() can access it> > static> class> Node {> > int> data;> > Node next;> > // Constructor> > Node(> int> d)> > {> > data = d;> > next => null> ;> > }> > }> > // Method to insert a new node> > public> static> LinkedList insert(LinkedList list,> > int> data)> > {> > // Create a new node with given data> > Node new_node => new> Node(data);> > new_node.next => null> ;> > // If the Linked List is empty,> > // then make the new node as head> > if> (list.head ==> null> ) {> > list.head = new_node;> > }> > else> {> > // Else traverse till the last node> > // and insert the new_node there> > Node last = list.head;> > while> (last.next !=> null> ) {> > last = last.next;> > }> > // Insert the new_node at last node> > last.next = new_node;> > }> > // Return the list by head> > return> list;> > }> > // Method to print the LinkedList.> > public> static> void> printList(LinkedList list)> > {> > Node currNode = list.head;> > System.out.print(> 'LinkedList: '> );> > // Traverse through the LinkedList> > while> (currNode !=> null> ) {> > // Print the data at current node> > System.out.print(currNode.data +> ' '> );> > // Go to next node> > currNode = currNode.next;> > }> > System.out.println();> > }> > // Method to delete a node in the LinkedList by POSITION> > public> static> LinkedList> > deleteAtPosition(LinkedList list,> int> index)> > {> > // Store head node> > Node currNode = list.head, prev => null> ;> > //> > // CASE 1:> > // If index is 0, then head node itself is to be> > // deleted> > if> (index ==> 0> && currNode !=> null> ) {> > list.head = currNode.next;> // Changed head> > // Display the message> > System.out.println(> > index +> ' position element deleted'> );> > // Return the updated List> > return> list;> > }> > //> > // CASE 2:> > // If the index is greater than 0 but less than the> > // size of LinkedList> > //> > // The counter> > int> counter => 0> ;> > // Count for the index to be deleted,> > // keep track of the previous node> > // as it is needed to change currNode.next> > while> (currNode !=> null> ) {> > if> (counter == index) {> > // Since the currNode is the required> > // position Unlink currNode from linked list> > prev.next = currNode.next;> > // Display the message> > System.out.println(> > index +> ' position element deleted'> );> > break> ;> > }> > else> {> > // If current position is not the index> > // continue to next node> > prev = currNode;> > currNode = currNode.next;> > counter++;> > }> > }> > // If the position element was found, it should be> > // at currNode Therefore the currNode shall not be> > // null> > //> > // CASE 3: The index is greater than the size of the> > // LinkedList> > //> > // In this case, the currNode should be null> > if> (currNode ==> null> ) {> > // Display the message> > System.out.println(> > index +> ' position element not found'> );> > }> > // return the List> > return> list;> > }> > // **************MAIN METHOD**************> > // method to create a Singly linked list with n nodes> > public> static> void> main(String[] args)> > {> > /* Start with the empty list. */> > LinkedList list => new> LinkedList();> > //> > // ******INSERTION******> > //> > // Insert the values> > list = insert(list,> 1> );> > list = insert(list,> 2> );> > list = insert(list,> 3> );> > list = insert(list,> 4> );> > list = insert(list,> 5> );> > list = insert(list,> 6> );> > list = insert(list,> 7> );> > list = insert(list,> 8> );> > // Print the LinkedList> > printList(list);> > //> > // ******DELETION AT POSITION******> > //> > // Delete node at position 0> > // In this case the key is ***at head***> > deleteAtPosition(list,> 0> );> > // Print the LinkedList> > printList(list);> > // Delete node at position 2> > // In this case the key is present ***in the> > // middle***> > deleteAtPosition(list,> 2> );> > // Print the LinkedList> > printList(list);> > // Delete node at position 10> > // In this case the key is ***not present***> > deleteAtPosition(list,> 10> );> > // Print the LinkedList> > printList(list);> > }> }>

Ieșire

LinkedList: 1 2 3 4 5 6 7 8 0 position element deleted LinkedList: 2 3 4 5 6 7 8 2 position element deleted LinkedList: 2 3 5 6 7 8 10 position element not found LinkedList: 2 3 5 6 7 8 

Toate operațiunile:

Mai jos este programul complet care aplică fiecare operație împreună:

Java

import> java.io.*;> // Java program to implement> // a Singly Linked List> public> class> LinkedList {> > Node head;> // head of list> > // Linked list Node.> > // Node is a static nested class> > // so main() can access it> > static> class> Node {> > int> data;> > Node next;> > // Constructor> > Node(> int> d)> > {> > data = d;> > next => null> ;> > }> > }> > // **************INSERTION**************> > // Method to insert a new node> > public> static> LinkedList insert(LinkedList list,> > int> data)> > {> > // Create a new node with given data> > Node new_node => new> Node(data);> > new_node.next => null> ;> > // If the Linked List is empty,> > // then make the new node as head> > if> (list.head ==> null> ) {> > list.head = new_node;> > }> > else> {> > // Else traverse till the last node> > // and insert the new_node there> > Node last = list.head;> > while> (last.next !=> null> ) {> > last = last.next;> > }> > // Insert the new_node at last node> > last.next = new_node;> > }> > // Return the list by head> > return> list;> > }> > // **************TRAVERSAL**************> > // Method to print the LinkedList.> > public> static> void> printList(LinkedList list)> > {> > Node currNode = list.head;> > System.out.print(> ' LinkedList: '> );> > // Traverse through the LinkedList> > while> (currNode !=> null> ) {> > // Print the data at current node> > System.out.print(currNode.data +> ' '> );> > // Go to next node> > currNode = currNode.next;> > }> > System.out.println(> ' '> );> > }> > // **************DELETION BY KEY**************> > // Method to delete a node in the LinkedList by KEY> > public> static> LinkedList deleteByKey(LinkedList list,> > int> key)> > {> > // Store head node> > Node currNode = list.head, prev => null> ;> > //> > // CASE 1:> > // If head node itself holds the key to be deleted> > if> (currNode !=> null> && currNode.data == key) {> > list.head = currNode.next;> // Changed head> > // Display the message> > System.out.println(key +> ' found and deleted'> );> > // Return the updated List> > return> list;> > }> > //> > // CASE 2:> > // If the key is somewhere other than at head> > //> > // Search for the key to be deleted,> > // keep track of the previous node> > // as it is needed to change currNode.next> > while> (currNode !=> null> && currNode.data != key) {> > // If currNode does not hold key> > // continue to next node> > prev = currNode;> > currNode = currNode.next;> > }> > // If the key was present, it should be at currNode> > // Therefore the currNode shall not be null> > if> (currNode !=> null> ) {> > // Since the key is at currNode> > // Unlink currNode from linked list> > prev.next = currNode.next;> > // Display the message> > System.out.println(key +> ' found and deleted'> );> > }> > //> > // CASE 3: The key is not present> > //> > // If key was not present in linked list> > // currNode should be null> > if> (currNode ==> null> ) {> > // Display the message> > System.out.println(key +> ' not found'> );> > }> > // return the List> > return> list;> > }> > // **************DELETION AT A POSITION**************> > // Method to delete a node in the LinkedList by POSITION> > public> static> LinkedList> > deleteAtPosition(LinkedList list,> int> index)> > {> > // Store head node> > Node currNode = list.head, prev => null> ;> > //> > // CASE 1:> > // If index is 0, then head node itself is to be> > // deleted> > if> (index ==> 0> && currNode !=> null> ) {> > list.head = currNode.next;> // Changed head> > // Display the message> > System.out.println(> > index +> ' position element deleted'> );> > // Return the updated List> > return> list;> > }> > //> > // CASE 2:> > // If the index is greater than 0 but less than the> > // size of LinkedList> > //> > // The counter> > int> counter => 0> ;> > // Count for the index to be deleted,> > // keep track of the previous node> > // as it is needed to change currNode.next> > while> (currNode !=> null> ) {> > if> (counter == index) {> > // Since the currNode is the required> > // position Unlink currNode from linked list> > prev.next = currNode.next;> > // Display the message> > System.out.println(> > index +> ' position element deleted'> );> > break> ;> > }> > else> {> > // If current position is not the index> > // continue to next node> > prev = currNode;> > currNode = currNode.next;> > counter++;> > }> > }> > // If the position element was found, it should be> > // at currNode Therefore the currNode shall not be> > // null> > //> > // CASE 3: The index is greater than the size of the> > // LinkedList> > //> > // In this case, the currNode should be null> > if> (currNode ==> null> ) {> > // Display the message> > System.out.println(> > index +> ' position element not found'> );> > }> > // return the List> > return> list;> > }> > // **************MAIN METHOD**************> > // method to create a Singly linked list with n nodes> > public> static> void> main(String[] args)> > {> > /* Start with the empty list. */> > LinkedList list => new> LinkedList();> > //> > // ******INSERTION******> > //> > // Insert the values> > list = insert(list,> 1> );> > list = insert(list,> 2> );> > list = insert(list,> 3> );> > list = insert(list,> 4> );> > list = insert(list,> 5> );> > list = insert(list,> 6> );> > list = insert(list,> 7> );> > list = insert(list,> 8> );> > // Print the LinkedList> > printList(list);> > //> > // ******DELETION BY KEY******> > //> > // Delete node with value 1> > // In this case the key is ***at head***> > deleteByKey(list,> 1> );> > // Print the LinkedList> > printList(list);> > // Delete node with value 4> > // In this case the key is present ***in the> > // middle***> > deleteByKey(list,> 4> );> > // Print the LinkedList> > printList(list);> > // Delete node with value 10> > // In this case the key is ***not present***> > deleteByKey(list,> 10> );> > // Print the LinkedList> > printList(list);> > //> > // ******DELETION AT POSITION******> > //> > // Delete node at position 0> > // In this case the key is ***at head***> > deleteAtPosition(list,> 0> );> > // Print the LinkedList> > printList(list);> > // Delete node at position 2> > // In this case the key is present ***in the> > // middle***> > deleteAtPosition(list,> 2> );> > // Print the LinkedList> > printList(list);> > // Delete node at position 10> > // In this case the key is ***not present***> > deleteAtPosition(list,> 10> );> > // Print the LinkedList> > printList(list);> > }> }>

Ieșire

LinkedList: 1 2 3 4 5 6 7 8 1 found and deleted LinkedList: 2 3 4 5 6 7 8 4 found and deleted LinkedList: 2 3 5 6 7 8 10 not found LinkedList: 2 3 5 6 7 8 0 position element deleted LinkedList: 3 5 6 7 8 2 position element deleted LinkedList: 3 5 7 8 10 position element not found LinkedList: 3 5 7 8