Menu driven program for all operations on singly linked list in C

// C program for the all operations in
// the Singly Linked List

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

// Linked List Node
struct node {
    int info;
    struct node* link;
};
struct node* start = NULL;

// Function to create list with n nodes initially
void createList()
{
    if (start == NULL) {
        int n;
        printf("\nEnter the number of nodes: ");
        scanf("%d", &n);
        if (n != 0) {
            int data;
            struct node* newnode;
            struct node* temp;
            newnode = malloc(sizeof(struct node));
            newnode->link = NULL;
            start = newnode;
            temp = start;
            printf("\nEnter number to"
                   " be inserted : ");
            scanf("%d", &data);
            start->info = data;

            for (int i = 2; i <= n; i++) {
                newnode = malloc(sizeof(struct node));
                newnode->link = NULL;
                temp->link = newnode;
                printf("\nEnter number to"
                       " be inserted : ");
                scanf("%d", &data);
                newnode->info = data;
                temp = temp->link;
            }
        }
        printf("\nThe list is created\n");
    }
    else
        printf("\nThe list is already created\n");
}

// Function to traverse the linked list
void traverse()
{
    struct node* temp;

    // List is empty
    if (start == NULL)
        printf("\nList is empty\n");

    // Else print the LL
    else {
        temp = start;
        while (temp != NULL) {
            printf("Data = %d\n", temp->info);
            temp = temp->link;
        }
    }
}

// Function to insert at the front
// of the linked list
void insertAtFront()
{
    int data;
    struct node* temp;
    temp = malloc(sizeof(struct node));
    printf("\nEnter number to"
           " be inserted : ");
    scanf("%d", &data);
    temp->info = data;

    // Pointer of temp will be
    // assigned to start
    temp->link = start;
    start = temp;
}

// Function to insert at the end of
// the linked list
void insertAtEnd()
{
    int data;
    struct node *temp, *head;
    temp = malloc(sizeof(struct node));

    // Enter the number
    printf("\nEnter number to"
           " be inserted : ");
    scanf("%d", &data);

    // Changes links
    temp->link = 0;
    temp->info = data;
    head = start;
    while (head->link != NULL) {
        head = head->link;
    }
    head->link = temp;
}

// Function to insert at any specified
// position in the linked list
void insertAtPosition()
{
    struct node *temp, *newnode;
    int pos, data, i = 1;
    newnode = malloc(sizeof(struct node));

    // Enter the position and data
    printf("\nEnter position and data :");
    scanf("%d %d", &pos, &data);

    // Change Links
    temp = start;
    newnode->info = data;
    newnode->link = 0;
    while (i < pos - 1) {
        temp = temp->link;
        i++;
    }
    newnode->link = temp->link;
    temp->link = newnode;
}

// Function to delete from the front
// of the linked list
void deleteFirst()
{
    struct node* temp;
    if (start == NULL)
        printf("\nList is empty\n");
    else {
        temp = start;
        start = start->link;
        free(temp);
    }
}

// Function to delete from the end
// of the linked list
void deleteEnd()
{
    struct node *temp, *prevnode;
    if (start == NULL)
        printf("\nList is Empty\n");
    else {
        temp = start;
        while (temp->link != 0) {
            prevnode = temp;
            temp = temp->link;
        }
        free(temp);
        prevnode->link = 0;
    }
}

// Function to delete from any specified
// position from the linked list
void deletePosition()
{
    struct node *temp, *position;
    int i = 1, pos;

    // If LL is empty
    if (start == NULL)
        printf("\nList is empty\n");

    // Otherwise
    else {
        printf("\nEnter index : ");

        // Position to be deleted
        scanf("%d", &pos);
        position = malloc(sizeof(struct node));
        temp = start;

        // Traverse till position
        while (i < pos - 1) {
            temp = temp->link;
            i++;
        }

        // Change Links
        position = temp->link;
        temp->link = position->link;

        // Free memory
        free(position);
    }
}

// Function to find the maximum element
// in the linked list
void maximum()
{
    int a[10];
    int i;
    struct node* temp;

    // If LL is empty
    if (start == NULL)
        printf("\nList is empty\n");

    // Otherwise
    else {
        temp = start;
        int max = temp->info;

        // Traverse LL and update the
        // maximum element
        while (temp != NULL) {

            // Update the maximum
            // element
            if (max < temp->info)
                max = temp->info;
            temp = temp->link;
        }
        printf("\nMaximum number "
               "is : %d ",
               max);
    }
}

// Function to find the mean of the
// elements in the linked list
void mean()
{
    int a[10];
    int i;
    struct node* temp;

    // If LL is empty
    if (start == NULL)
        printf("\nList is empty\n");

    // Otherwise
    else {
        temp = start;

        // Stores the sum and count of
        // element in the LL
        int sum = 0, count = 0;
        float m;

        // Traverse the LL
        while (temp != NULL) {

            // Update the sum
            sum = sum + temp->info;
            temp = temp->link;
            count++;
        }

        // Find the mean
        m = sum / count;

        // Print the mean value
        printf("\nMean is %f ", m);
    }
}

// Function to sort the linked list
// in ascending order
void sort()
{
    struct node* current = start;
    struct node* index = NULL;
    int temp;

    // If LL is empty
    if (start == NULL) {
        return;
    }

    // Else
    else {

        // Traverse the LL
        while (current != NULL) {
            index = current->link;

            // Traverse the LL nestedly
            // and find the minimum
            // element
            while (index != NULL) {

                // Swap with it the value
                // at current
                if (current->info > index->info) {
                    temp = current->info;
                    current->info = index->info;
                    index->info = temp;
                }
                index = index->link;
            }

            // Update the current
            current = current->link;
        }
    }
}

// Function to reverse the linked list
void reverseLL()
{
    struct node *t1, *t2, *temp;
    t1 = t2 = NULL;

    // If LL is empty
    if (start == NULL)
        printf("List is empty\n");

    // Else
    else {

        // Traverse the LL
        while (start != NULL) {

            // reversing of points
            t2 = start->link;
            start->link = t1;
            t1 = start;
            start = t2;
        }
        start = t1;

        // New head Node
        temp = start;

        printf("Reversed linked "
               "list is : ");

        // Print the LL
        while (temp != NULL) {
            printf("%d ", temp->info);
            temp = temp->link;
        }
    }
}

// Function to search an element in linked list
void search()
{
    int found = -1;
    // creating node to traverse
    struct node* tr = start;

    // first checking if the list is empty or not
    if (start == NULL) {
        printf("Linked list is empty\n");
    }
    else {
        printf("\nEnter the element you want to search: ");
        int key;
        scanf("%d", &key);

        // checking by traversing
        while (tr != NULL) {
            // checking for key
            if (tr->info == key) {
                found = 1;
                break;
            }
            // moving forward if not at this position
            else {
                tr = tr->link;
            }
        }

        // printing found or not
        if (found == 1) {
            printf(
                "Yes, %d is present in the linked list.\n",
                key);
        }
        else {
            printf("No, %d is not present in the linked "
                   "list.\n",
                   key);
        }
    }
}

// Driver Code
int main()
{
    createList();
    int choice;
    while (1) {

        printf("\n\t1 To see list\n");
        printf("\t2 For insertion at"
               " starting\n");
        printf("\t3 For insertion at"
               " end\n");
        printf("\t4 For insertion at "
               "any position\n");
        printf("\t5 For deletion of "
               "first element\n");
        printf("\t6 For deletion of "
               "last element\n");
        printf("\t7 For deletion of "
               "element at any position\n");
        printf("\t8 To find maximum among"
               " the elements\n");
        printf("\t9 To find mean of "
               "the elements\n");
        printf("\t10 To sort element\n");
        printf("\t11 To reverse the "
               "linked list\n");
        printf("\t12 Search an element in linked list\n");
        printf("\t13 To exit\n");
        printf("\nEnter Choice :\n");
        scanf("%d", &choice);

        switch (choice) {
        case 1:
            traverse();
            break;
        case 2:
            insertAtFront();
            break;
        case 3:
            insertAtEnd();
            break;
        case 4:
            insertAtPosition();
            break;
        case 5:
            deleteFirst();
            break;
        case 6:
            deleteEnd();
            break;
        case 7:
            deletePosition();
            break;
        case 8:
            maximum();
            break;
        case 9:
            mean();
            break;
        case 10:
            sort();
            break;
        case 11:
            reverseLL();
            break;
        case 12:
            search();
            break;
        case 13:
            exit(1);
            break;
        default:
            printf("Incorrect Choice\n");
        }
    }
    return 0;
}