Reversing singly Linked List - Explanation

I have searched some sites to know how they are reversing linked list , yeah I found so many sites but none of them are explained . So , I conclude it  to do in my blog



Below are the working piece of code 

 #include <iostream.h>  
 #include <conio.h>  
 class Node  
 {  
  public:  
    int data ;  
    Node * next ;   
    Node(int in){data = in; }   // public param cons  
    };  
 Node* Reverse(Node * head )  
  {  
      Node * temp = NULL ;  
      Node * np = NULL;  
     while (head)  
      {  
       temp = head->next;  
       head->next = np;  
       np = head ;  
       head = temp;     
      }  
      return np ;  
  }  
  void Display(Node * head )  
   {  
    while (head)  
    {  
     printf("%d \t" , head->data);  
     head = head-> next ;    
    }  
   }  
 main()  
 {  
   Node * obj1= new Node(10) ;  
   Node * obj2= new Node(20) ;  
   Node * obj3= new Node(30) ;  
   Node * obj4= new Node(40) ;  
   obj1->next = obj2 ;  
   obj2->next = obj3 ;  
   obj3->next = obj4 ;  
   printf("Before reversing ");    
   Display(obj1);    
   Node * head = Reverse(obj1);  
   printf("\n After reversing ");    
   Display(head);  
   getch();    
 }  

Lets see the explanation of Important lines 
  before getting in to that , you need two variable
1. temp -> used to hold next element pointer and given back the address to head
2. np    -> Assign it to head->next

lets discuss the code line by line

step1 :        temp = head->next;   
 take the information of next , so that we can play with head->next

step2:        head->next = np ;
 yeah , In the next line we are changing head->next  ( anyway we are having this info intemp   for later use)
initially np  is null , but from the second iteration it has the info of prev element

step3:       np = head ; 
yeh , this step does the same what we want in step 2

step4:    head = temp ;

finally head should move to next element . fortunately this info is stored in temp 


thats all dudes , np will become your new head pointer .

 It may not be the great explanation , but it will be used to the beginners .