What is a Singly Linked List?

A Singly Linked List is a linear data structure where elements (nodes) are stored in heap memory. Each node contains:

1. data: The value stored in the node.
2. next: A pointer pointing to the next node in the sequence.

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Complete C Implementation

c (ISO Standard)
Run in Compiler.cCopy
#include <stdio.h>
#include <stdlib.h>

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

Node* createNode(int value) {
    Node *newNode = (Node*)malloc(sizeof(Node));
    if (newNode == NULL) {
        fprintf(stderr, "Memory allocation failed.\n");
        exit(EXIT_FAILURE);
    }
    newNode->data = value;
    newNode->next = NULL;
    return newNode;
}

void insertAtHead(Node **head, int value) {
    Node *newNode = createNode(value);
    newNode->next = *head;
    *head = newNode;
}

void printList(const Node *head) {
    const Node *current = head;
    while (current != NULL) {
        printf("%d -> ", current->data);
        current = current->next;
    }
    printf("NULL\n");
}

void freeList(Node *head) {
    Node *temp;
    while (head != NULL) {
        temp = head;
        head = head->next;
        free(temp);
    }
}

int main() {
    Node *head = NULL;

    printf("Building Singly Linked List in C:\n");
    insertAtHead(&head, 40);
    insertAtHead(&head, 30);
    insertAtHead(&head, 20);
    insertAtHead(&head, 10);

    printList(head);

    freeList(head);
    return 0;
}

Sample Output

text (ISO Standard)
Copy
Building Singly Linked List in C:
10 -> 20 -> 30 -> 40 -> NULL

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Complexity Analysis

• Insert at Head: O(1) constant time.
• Traversal & Search: O(n) linear time.
• Space Overhead: Requires 1 pointer per node on 64-bit systems (8 bytes per pointer).

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Related Data Structures & Guides

• Master structures and pointer members in Structures in C.
• Master dynamic memory in Pointers in C.