Ordered and Unordered Singly Linked Lists in C

What is a Singly Linked List in C?

A singly linked list is a linear data structure where each node contains two parts:

Data – the value or information stored.
Pointer (next) – a reference to the next node in the list.

Here’s how a single node looks in C:

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

The list starts from a special pointer called head, which points to the first node. If the list is empty, head is NULL.

Types of Singly Linked Lists

Unordered Singly Linked List – No order is maintained while inserting.
Ordered Singly Linked List – Elements are inserted in sorted (ascending/descending) order.

Unordered Singly Linked List

An unordered singly linked list does not maintain any specific order among its elements.

Insertion at Beginning

void insert_unordered(struct quiz **head, int value) {
    struct quiz *newNode = (struct quiz *)malloc(sizeof(struct quiz));
    newNode->data = value;
    newNode->next = *head;
    *head = newNode;
}

Traversal

void traverse_list(struct quiz *head) {
    while (head != NULL) {
        printf("%d -> ", head->data);
        head = head->next;
    }
    printf("NULL\n");
}

Deletion of a Node

void delete_unordered(struct quiz **head, int key) {
    struct quiz *temp = *head, *prev = NULL;
 
    if (temp != NULL && temp->data == key) {
        *head = temp->next;
        free(temp);
        return;
    }
 
    while (temp != NULL && temp->data != key) {
        prev = temp;
        temp = temp->next;
    }
 
    if (temp == NULL) return;
 
    prev->next = temp->next;
    free(temp);
}

Example – Unordered Singly Linked List

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int main() {
    struct quiz *certification = NULL;
 
    insert_unordered(&certification, 30);
    insert_unordered(&certification, 10);
    insert_unordered(&certification, 20);
 
    printf("Unordered Linked List:\n");
    traverse_list(certification);
 
    delete_unordered(&certification, 10);
    printf("After Deletion:\n");
    traverse_list(certification);
 
    return 0;
}

Ordered Singly Linked List (Ascending)

An ordered singly linked list maintains its elements in a sorted manner, typically in ascending order.

Insertion in Sorted Order

void insert_ordered(struct quiz **head, int value) {
    struct quiz *newNode = (struct quiz *)malloc(sizeof(struct quiz));
    newNode->data = value;
    newNode->next = NULL;
 
    if (*head == NULL || (*head)->data >= value) {
        newNode->next = *head;
        *head = newNode;
    } else {
        struct quiz *current = *head;
        while (current->next != NULL && current->next->data < value) {
            current = current->next;
        }
        newNode->next = current->next;
        current->next = newNode;
    }
}

Traversal (Same as Before)

void traverse_list(struct quiz *head) {
    while (head != NULL) {
        printf("%d -> ", head->data);
        head = head->next;
    }
    printf("NULL\n");
}

Example – Ordered Singly Linked List

int main() {
    struct quiz *test = NULL;
 
    insert_ordered(&test, 50);
    insert_ordered(&test, 10);
    insert_ordered(&test, 30);
 
    printf("Ordered Linked List:\n");
    traverse_list(test);
 
    return 0;
}

Ordered vs. Unordered Singly Linked Lists

Feature	Ordered List	Unordered List
Order of elements	Sorted (e.g., ascending order)	No specific order
Insertion logic	Insert in sorted position	Insert at head or end
Search efficiency	Can break early during search	Must scan full list
Use case	When order matters	When speed of insert matters

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Related Posts:

What is a Singly Linked List in C?

Types of Singly Linked Lists

Unordered Singly Linked List

Ordered Singly Linked List (Ascending)

Ordered vs. Unordered Singly Linked Lists

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