linkList.c

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

struct node {
    int data;
    int key;
    struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// Display the list
void printList() {
    struct node *ptr = head;
    printf("\n[ ");

    // Start from the beginning
    while (ptr != NULL) {
        printf("(%d, %d) ", ptr->key, ptr->data);
        ptr = ptr->next;
    }
    printf(" ]");
}

// Insert link at the first location
void insertFirst(int key, int data) {
    // Create a link
    struct node *link = (struct node *)malloc(sizeof(struct node));
    link->key = key;
    link->data = data;

    // Point it to old first node
    link->next = head;

    // Point first to new first node
    head = link;
}

// Delete first item
struct node *deleFirst() {
    // Save reference to first link
    struct node *tempLink = head;

    // Mark next to first link as first
    head = head->next;

    // Return the deleted link
    return tempLink;
}

// Is list empty?
bool isEmpty() { return head == NULL; }

int length() {
    int length = 0;
    struct node *current;
    for (current = head; current != NULL; current = current->next) {
        ++length;
    }
    return length;
}

// Find a link with given key
struct node *find(int key) {
    // Start from the first link
    struct node *current = head;

    // If list is empty
    if (head == NULL) {
        return NULL;
    }

    // Navigate through list
    while (current->key != key) {
        // If is is last node
        if (current->next == NULL) {
            return NULL;
        } else {
            // Go to next link
            current = current->next;
        }
    }
    // If data found, return the current link
    return current;
}

// Delete a link with given key
struct node *delete(int key) {
    // Start from the first link
    struct node *current = head;
    struct node *previous = NULL;

    // If list is empty
    if (head == NULL) {
        return NULL;
    }
    // Navigate through list
    while (current->key != key) {
        // If it is last node
        if (current->next == NULL) {
            return NULL;
        } else {
            // Store reference to current link
            previous = current;

            // Move to next link
            current = current->next;
        }
    }

    // Found a match, update the link
    if (current == head) {
        // Change first to point to next link
        head = head->next;
    } else {
        // Bypass the current link
        previous->next = current->next;
    }

    return current;
}

void sort() {
    int i, j, k, tempKey, tempData;
    struct node *current;
    struct node *next;
    int size = length();
    k = size;
    for (i = 0; i < size - 1; ++i, --k) {
        current = head;
        next = head->next;
        for (j = 1; j < k; ++j) {
            if (current->data > next->data) {
                tempData = current->data;
                current->data = next->data;
                next->data = tempData;

                tempKey = current->key;
                current->key = next->key;
                next->key = tempKey;
            }

            current = current->next;
            next = next->next;
        }
    }
}

void reverse(struct node **head_ref) {
    struct node *prev = NULL;
    struct node *current = *head_ref;
    struct node *next;
    while (current != NULL) {
        next = current->next;
        current->next = prev;
        prev = current;
        current = next;
    }
    *head_ref = prev;
}

int main() {
    insertFirst(1, 10);
    insertFirst(2, 20);
    insertFirst(3, 30);
    insertFirst(4, 1);
    insertFirst(5, 40);
    insertFirst(6, 56);

    printf("Original List: ");
    // Print list
    printList();

    while (!isEmpty()) {
        struct node *temp = deleFirst();
        printf("\nDeleted value:");
        printf("(%d,%d) ", temp->key, temp->data);
    }
    printf("\nList after deleting all items: ");
    printList();
    insertFirst(1, 10);
    insertFirst(2, 20);
    insertFirst(3, 30);
    insertFirst(4, 1);
    insertFirst(5, 40);
    insertFirst(6, 56);
    printf("\nRestored List: ");
    printList();
    printf("\n");

    struct node *foundLink = find(4);
    if (foundLink != NULL) {
        printf("Element found: ");
        printf("(%d,%d) ", foundLink->key, foundLink->data);
        printf("\n");
    } else {
        printf("Element not found.");
    }
    delete (4);
    printf("List after deleting an item: ");
    printList();
    printf("\n");
    foundLink = find(4);
    if (foundLink != NULL) {
        printf("Element found: ");
        printf("(%d,%d) ", foundLink->key, foundLink->data);
        printf("\n");
    } else {
        printf("Element not found.");
    }
    printf("\n");
    sort();
    printf("List after sorting the data: ");
    printList();
    reverse(&head);
    printf("\nList after reversing the data: ");
    printList();
}