Answers for "Write a C program to implement a singly linked list and display it in reverse order"

reverse a singly linked list in c

/**
 * C program to reverse a Singly Linked List
 */

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


/* Structure of a node */
struct node {
    int data; //Data part
    struct node *next; //Address part
}*head;


/* Functions used in the program */
void createList(int n);
void reverseList();
void displayList();


int main()
{
    int n, choice;

    /*
     * Create a singly linked list of n nodes
     */
    printf("Enter the total number of nodes: ");
    scanf("%d", &n);
    createList(n);

    printf("\nData in the list \n");
    displayList();

    /*
     * Reverse the list
     */
    printf("\nPress 1 to reverse the order of singly linked list\n");
    scanf("%d", &choice);
    if(choice == 1)
    {
        reverseList();
    }

    printf("\nData in the list\n");
    displayList();

    return 0;
}


/*
 * Create a list of n nodes
 */
void createList(int n)
{
    struct node *newNode, *temp;
    int data, i;

    if(n <= 0)
    {
        printf("List size must be greater than zero.\n");
        return;
    }

    head = (struct node *)malloc(sizeof(struct node));

    /*
     * If unable to allocate memory for head node
     */
    if(head == NULL)
    {
        printf("Unable to allocate memory.");
    }
    else
    {
        /*
         * Read data of node from the user
         */
        printf("Enter the data of node 1: ");
        scanf("%d", &data);

        head->data = data; // Link the data field with data
        head->next = NULL; // Link the address field to NULL

        temp = head;

        /*
         * Create n nodes and adds to linked list
         */
        for(i=2; i<=n; i++)
        {
            newNode = (struct node *)malloc(sizeof(struct node));

            /* If memory is not allocated for newNode */
            if(newNode == NULL)
            {
                printf("Unable to allocate memory.");
                break;
            }
            else
            {
                printf("Enter the data of node %d: ", i);
                scanf("%d", &data);

                newNode->data = data; // Link the data field of newNode with data
                newNode->next = NULL; // Link the address field of newNode with NULL

                temp->next = newNode; // Link previous node i.e. temp to the newNode
                temp = temp->next;
            }
        }

        printf("SINGLY LINKED LIST CREATED SUCCESSFULLY\n");
    }
}


/*
 * Reverse the order of nodes of a singly linked list
 */
void reverseList()
{
    struct node *prevNode, *curNode;

    if(head != NULL)
    {
        prevNode = head;
        curNode = head->next;
        head = head->next;

        prevNode->next = NULL; // Make first node as last node

        while(head != NULL)
        {
            head = head->next;
            curNode->next = prevNode;

            prevNode = curNode;
            curNode = head;
        }

        head = prevNode; // Make last node as head

        printf("SUCCESSFULLY REVERSED LIST\n");
    }
}


/*
 * Display entire list
 */
void displayList()
{
    struct node *temp;

    /*
     * If the list is empty i.e. head = NULL
     */
    if(head == NULL)
    {
        printf("List is empty.");
    }
    else
    {
        temp = head;
        while(temp != NULL)
        {
            printf("Data = %d\n", temp->data); // Print the data of current node
            temp = temp->next;                 // Move to next node
        }
    }
}

Write a C program to implement a singly linked list and display it in reverse order

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

struct node 
{
    int num;                    //Data of the node
    struct node *nextptr;       //Address of the node
}*stnode;

void createNodeList(int n);     //function to create the list
void reverseDispList();         //function to convert the list in reverse
void displayList();             //function to display the list

int main()
{
    int n;
		printf("\n\n Linked List : Create a singly linked list and print it in reverse order :\n");
		printf("------------------------------------------------------------------------------\n");
		
    printf(" Input the number of nodes : ");
    scanf("%d", &n);
    createNodeList(n);
    printf("\n Data entered in the list are : \n");		
    displayList();
    reverseDispList();
    printf("\n The list in reverse are :  \n");
    displayList();
    return 0;
}

void createNodeList(int n)
{
    struct node *fnNode, *tmp;
    int num, i;
    stnode = (struct node *)malloc(sizeof(struct node));
    if(stnode == NULL) //check whether the stnode is NULL and if so no memory allocation
    {
        printf(" Memory can not be allocated.");
    }
    else
    {
// reads data for the node through keyboard
        printf(" Input data for node 1 : ");
        scanf("%d", &num);
        stnode-> num = num;      
        stnode-> nextptr = NULL; //Links the address field to NULL
        tmp = stnode;
//Creates n nodes and adds to linked list
        for(i=2; i<=n; i++)
        {
            fnNode = (struct node *)malloc(sizeof(struct node));
            if(fnNode == NULL) //check whether the fnnode is NULL and if so no memory allocation
            {
                printf(" Memory can not be allocated.");
                break;
            }
            else
            {
                printf(" Input data for node %d : ", i);
                scanf(" %d", &num);
                fnNode->num = num;      // links the num field of fnNode with num
                fnNode->nextptr = NULL; // links the address field of fnNode with NULL
                tmp->nextptr = fnNode; // links previous node i.e. tmp to the fnNode
                tmp = tmp->nextptr;
            }
        }
    }
}

void reverseDispList()
{
    struct node *prevNode, *curNode;
 
    if(stnode != NULL)
    {
        prevNode = stnode;
        curNode = stnode->nextptr;
        stnode = stnode->nextptr;
 
        prevNode->nextptr = NULL; //convert the first node as last
 
        while(stnode != NULL)
        {
            stnode = stnode->nextptr;
            curNode->nextptr = prevNode;
 
            prevNode = curNode;
            curNode = stnode;
        }
        stnode = prevNode; //convert the last node as head
    }
}

void displayList()
{
    struct node *tmp;
    if(stnode == NULL)
    {
        printf(" No data found in the list.");
    }
    else
    {
        tmp = stnode;
        while(tmp != NULL)
        {
            printf(" Data = %d\n", tmp->num);   // prints the data of current node
            tmp = tmp->nextptr;                 // advances the position of current node
        }
    }
}

reverse linked list in c

#include <stdio.h>
struct Node {
   int data;
   struct Node* next;
   Node(int data){
      this->data = data;
      next = NULL;
   }
};
struct LinkedList {
   Node* head;
   LinkedList(){
      head = NULL;
   }
   void interReverseLL(){
      Node* current = head;
      Node *prev = NULL, *after = NULL;
      while (current != NULL) {
         after = current->next;
         current->next = prev;
         prev = current;
         current = after;
      }
      head = prev;
   }
   void print() {
      struct Node* temp = head;
      while (temp != NULL) {
         printf("%d ", temp-> data);
         temp = temp->next;
      }
      printf("\n");
   }
   void push(int data){
      Node* temp = new Node(data);
      temp->next = head;
      head = temp;
   }
};
int main() {
   LinkedList linkedlist;
   linkedlist.push(85);
   linkedlist.push(10);
   linkedlist.push(65);
   linkedlist.push(32);
   linkedlist.push(9);
   printf("Linked List : \t");
   linkedlist.print();
   linkedlist.interReverseLL();
   printf("Reverse Linked List : \t");
   linkedlist.print();
   return 0;
}


Output
Linked List : 9 32 65 10 85
Reverse Linked List : 85 10 65 32 9