Linked List Overview

linked list is a linear data structure where each element is a separate object. Linked list elements are not stored at contiguous location; the elements are linked using pointers. Each node of a list is made up of two items - the data and a reference to the next node. The last node has a reference to null.

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

/* Link list node */
struct node
{
    int data;
    struct node* next;
};
 node * reverse1( node * ptr , node * previous) //with recursion
{
    node * temp;
    if(ptr->next == NULL) {
        ptr->next = previous;
        return ptr;
    } else {
        temp = reverse1(ptr->next, ptr);
        ptr->next = previous;
        return temp;
    }
}
/* Function to reverse the linked list */
static void reverse(struct node** head_ref)  //without recursion
{
    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;
}

/* Function to push a node */
void push(struct node** head_ref, int new_data)
{
    /* allocate node */
    struct node* new_node =
            (struct node*) malloc(sizeof(struct node));
           
    /* put in the data  */
    new_node->data  = new_data;
               
    /* link the old list off the new node */
    new_node->next = (*head_ref);   
       
    /* move the head to point to the new node */
    (*head_ref)    = new_node;
}

/* Function to print linked list */
void printList(struct node *head)
{
    struct node *temp = head;
    while(temp != NULL)
    {
        printf("%d  ", temp->data);   
        temp = temp->next; 
    }
}   


int main()
{
    /* Start with the empty list */
    struct node* head = NULL;
  
     push(&head, 20);
     push(&head, 4);
     push(&head, 15);
     push(&head, 85);     
    
     printList(head);   
     head=reverse1(head,NULL);                     
     printf("\n Reversed Linked list \n");
     printList(head);   
  
    return 0;
}