You have to start somewhere, so we give the address of the first node a special name called HEAD . Also, the last node in the linked list can be identified because its next portion points to NULL .
Linked lists can be of multiple types: singly, doubly, and circular linked list. In this article, we will focus on the singly linked list. To learn about other types, visit Types of Linked List.
Note: You might have played the game Treasure Hunt, where each clue includes the information about the next clue. That is how the linked list operates.
Let's see how each node of the linked list is represented. Each node consists:
We wrap both the data item and the next node reference in a struct as:
struct node < int data; struct node *next; >;Understanding the structure of a linked list node is the key to having a grasp on it.
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.
/* Initialize nodes */ struct node *head; struct node *one = NULL; struct node *two = NULL; struct node *three = NULL; /* Allocate memory */ one = malloc(sizeof(struct node)); two = malloc(sizeof(struct node)); three = malloc(sizeof(struct node)); /* Assign data values */ one->data = 1; two->data = 2; three->data=3; /* Connect nodes */ one->next = two; two->next = three; three->next = NULL; /* Save address of first node in head */ head = one;If you didn't understand any of the lines above, all you need is a refresher on pointers and structs.
In just a few steps, we have created a simple linked list with three nodes.
The power of a linked list comes from the ability to break the chain and rejoin it. E.g. if you wanted to put an element 4 between 1 and 2, the steps would be:
Doing something similar in an array would have required shifting the positions of all the subsequent elements.
In python and Java, the linked list can be implemented using classes as shown in the codes below.
Lists are one of the most popular and efficient data structures, with implementation in every programming language like C, C++, Python, Java, and C#.
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.
# Linked list implementation in Python class Node: # Creating a node def __init__(self, item): self.item = item self.next = None class LinkedList: def __init__(self): self.head = None if __name__ == '__main__': linked_list = LinkedList() # Assign item values linked_list.head = Node(1) second = Node(2) third = Node(3) # Connect nodes linked_list.head.next = second second.next = third # Print the linked list item while linked_list.head != None: print(linked_list.head.item, end=" ") linked_list.head = linked_list.head.next // Linked list implementation in Java class LinkedList < // Creating a node Node head; static class Node < int value; Node next; Node(int d) < value = d; next = null; >> public static void main(String[] args) < LinkedList linkedList = new LinkedList(); // Assign value values linkedList.head = new Node(1); Node second = new Node(2); Node third = new Node(3); // Connect nodess linkedList.head.next = second; second.next = third; // printing node-value while (linkedList.head != null) < System.out.print(linkedList.head.value + " "); linkedList.head = linkedList.head.next; >> >// Linked list implementation in C #include #include // Creating a node struct node < int value; struct node *next; >; // print the linked list value void printLinkedlist(struct node *p) < while (p != NULL) < printf("%d ", p->value); p = p->next; > > int main() < // Initialize nodes struct node *head; struct node *one = NULL; struct node *two = NULL; struct node *three = NULL; // Allocate memory one = malloc(sizeof(struct node)); two = malloc(sizeof(struct node)); three = malloc(sizeof(struct node)); // Assign value values one->value = 1; two->value = 2; three->value = 3; // Connect nodes one->next = two; two->next = three; three->next = NULL; // printing node-value head = one; printLinkedlist(head); >// Linked list implementation in C++ #include #include using namespace std; // Creating a node class Node < public: int value; Node* next; >; int main() < Node* head; Node* one = NULL; Node* two = NULL; Node* three = NULL; // allocate 3 nodes in the heap one = new Node(); two = new Node(); three = new Node(); // Assign value values one->value = 1; two->value = 2; three->value = 3; // Connect nodes one->next = two; two->next = three; three->next = NULL; // print the linked list value head = one; while (head != NULL) < cout value; head = head->next; > >| Worst case | Average Case | |
|---|---|---|
| Search | O(n) | O(n) |
| Insert | O(1) | O(1) |
| Deletion | O(1) | O(1) |
Space Complexity: O(n)
