Implement Singly linked list (SLL) in C

Linked-List Operations in C

This code demonstrates various linked-list operations in C.

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

struct node
{
    int data;
    struct node *next;
} * head, *temp, *travel, *ptr;

void print()
{
    travel = head;
    if (travel == NULL)
    {
        printf("Linked-List is empty.\\n");
    }
    else
    {
        while (travel != NULL)
        {
            printf("%d ", travel->data);
            travel = travel->next;
        }
    }
}

void search(int key)
{
    int flag = 0;
    travel = head;
    if (travel == NULL)
    {
        printf("Linked-List is empty.\\n");
    }
    else
    {
        while (travel != NULL)
        {
            if ((travel->data) == key)
                flag = 1;
            else
                flag = 0;
            travel = travel->next;
        }
    }
    if (flag = 1)
        printf("\\nElement found..");
    else
        printf("\\nElement not found");
}

void add_at_begin(int data)
{
    ptr = (struct node *)malloc(sizeof(struct node));
    ptr->data = data;
    ptr->next = NULL;
    ptr->next = head;
    head = ptr;
}

void add_at_last(int data)
{
    struct node *new_node = (struct node *)malloc(sizeof(struct node));
    struct node *last = head;
    new_node->data = data;
    new_node->next = NULL;
    if (head == NULL)
    {
        head = new_node;
        return;
    }
    while (last->next != NULL)
        last = last->next;
    last->next = new_node;
}

void add_at_pos()
{
    int n, t;
    printf("\\nEnter the data of node that after you want to add the node:");
    scanf("%d", &n);
    printf("Enter the data to add in new node::");
    scanf("%d", &t);
    int loc = n;
    ptr = (struct node *)malloc(sizeof(struct node));
    ptr->data = t;
    temp = head;
    while (temp->data != loc)
    {
        temp = temp->next;
    }
    ptr->next = temp->next;
    temp->next = ptr;
}

void add_before()
{
    struct node *cur, *pre;
    cur = head;
    pre = head;
    int loc, new_data;
    ptr = (struct node *)malloc(sizeof(struct node));
    printf("\\nEnter the data that before you want to add the node::");
    scanf("%d", &loc);
    printf("Enter the data to add in new node::");
    scanf("%d", &new_data);
    ptr->data = new_data;
    while (cur->data != loc)
    {
        pre = cur;
        cur = cur->next;
    }
    pre->next = ptr;
    ptr->next = cur;
}

void del_first()
{
    if (head == NULL)
    {
        printf("\\nLinked-List is Empty..");
    }
    else
    {
        ptr = head;
        head = head->next;
        //free(ptr);
        //ptr= NULL;
    }
}

void del_last()
{
    struct node *cur, *pre;
    cur = head;
    pre = head;
    if (head == NULL)
        printf("Linked-list is empty");
    else if (head->next == NULL)
    {
        free(head);
        head = NULL;
    }
    while (cur->next != NULL)
    {
        pre = cur;
        cur = cur->next;
    }
    pre->next = NULL;
    free(cur);
}

void del_node()
{
    struct node *cur, *pre;
    int data;
    printf("\\nEnter the data of node that you want to delete::");
    scanf("%d", &data);
    cur = head;
    pre = head;
    while ((cur->data) != data)
    {
        pre = cur;
        cur = cur->next;
    }
    pre->next = cur->next;
    free(cur);
}

void main()
{
    int choice, n, t, key;
    while (1)
    {
        printf("\\n1.Insert a node at Start");
        printf("\\n2.Insert a node at Last");
        printf("\\n3.Insert a node at before data:");
        printf("\\n4.Insert a node at after data:");
        printf("\\n5.Display Linked-List");
        printf("\\n6.Delete  first node from Linked-List");
        printf("\\n7.Delete Last node from Linked-List");
        printf("\\n8.Delete Specific Node:");
        printf("\\n9.Exit");
        scanf("%d", &choice);
        switch (choice)
        {
        case 1:
            printf("Enter the data to add in new node::");
            scanf("%d", &t);
            add_at_begin(t);
            break;
        case 2:
            printf("Enter the data to add in new node::");
            scanf("%d", &t);
            add_at_last(t);
            break;
        case 3:
            add_before();
            break;
        case 4:
            add_at_pos();
            break;
        case 5:
            print();
            break;
        case 6:
            del_first();
            break;
        case 7:
            del_last();
            break;
        case 8:
            del_node();
            break;
        case 9:
            exit(0);
        default:
            printf("\\n\\aEnter valid choice");
            break;
        }
    }
}
    

This code implements various operations on a singly linked-list, including inserting nodes at the start and end, before and after specific data, and deleting nodes.

Feel free to experiment with this code and understand how each linked-list operation