Singly linked list in C

Data structures are crucial elements in computer programming because they make data handling and storage efficient. The linked list is a typical data structure. In this blog post, we will examine the concept of a single linked list in the C programming language. We'll go over its operations, definition, and example code syntax and outputs.

Each node in a singly linked list has a data element and a reference to the node after it in the list, making it a linear data structure. The list's head node is the first node, while the last node points to NULL to denote the list's end.

A structure for each list node must be constructed to define a single linked list in C. The structure should have two fields: a data field for storing the actual data and a pointer field for holding a reference to the subsequent node.

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

We must first initialize the head reference to NULL, which denotes an empty list, in order to establish a single linked list. After that, we may add nodes to the list by dynamically allocating memory for each node and connecting them with the next pointer.

struct Node* head = NULL;  // Initializing an empty list

void insert(int value) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
newNode->data = value;
newNode->next = NULL;

    if (head == NULL) {
        head = newNode;
    } else {
        struct Node* current = head;
        while (current->next != NULL) {
            current = current->next;
        }
        current->next = newNode;
    }
}

We must first initialize the head reference to NULL, which denotes an empty list, in order to establish a single linked list. After that, we may add nodes to the list by dynamically allocating memory for each node and connecting them with the next pointer.

void traverse() {
    struct Node* current = head;
    while (current != NULL) {
        printf("%d ", current->data);
        current = current->next;
    }
}

A singly linked list can be searched for an element by traversing the list and comparing each node's data with the desired value. If a match is made, the relevant node is returned; if not, NULL is returned to show that the element is not present in the list.

struct Node* search(int value) {
    struct Node* current = head;
    while (current != NULL) {
        if (current->data == value) {
            return current;
        }
        current = current->next;
    }
    return NULL;
}

To remove a component from a singly linked list, locate the node that contains the desired value and modify the links to the preceding and following nodes accordingly. Additionally, the memory that the destroyed node used must be freed.

void delete(int value) {
    if (head == NULL) {
        printf("List is empty.");
        return;
    }

    struct Node* current = head;
    struct Node* previous = NULL;

    while (current != NULL) {
        if (current->data == value) {
            if (previous == NULL) {
                head = current->next;
            } else {
                previous->next = current->next;
            }
            free(current);
            return;
        }
        previous = current;
        current = current->next;
    }

    printf("Element not found in the list.");
}

Example:

Let's create a list, add entries, and perform various operations on it to show how a single linked list is used.

#include <stdio.h>
#include <stdlib.h>

// Singly Linked List structure
struct Node {
    int data;
    struct Node* next;
};

// Global head pointer
struct Node* head = NULL;

// Function to insert a node at the end of the list
void insert(int value) {
    // Create a new node
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = value;
    newNode->next = NULL;

    // Check if the list is empty
    if (head == NULL) {
        head = newNode;
    } else {
        // Traverse to the end of the list
        struct Node* current = head;
        while (current->next != NULL) {
            current = current->next;
        }
        // Link the new node to the last node
        current->next = newNode;
    }
}

// Function to traverse and print the list
void traverse() {
    struct Node* current = head;
    while (current != NULL) {
        printf("%d ", current->data);
        current = current->next;
    }
}

int main() {
    // Insert elements into the list
    insert(10);
    insert(20);
    insert(30);
    insert(40);

    // Traverse and print the list
    printf("List: ");
    traverse();

    return 0;
}