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how to reverse link list using recurtion

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Join Date: Jun 2005

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happyshub

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how to reverse link list using recurtion

Jun 8th, 2005

please can someone give me code how to reverse single link list using recurtion

thanks

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long time no c

Re: how to reverse link list using recurtion

Jun 8th, 2005

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Originally Posted by happyshub

please can someone give me code how to reverse single link list using recurtion

Show an attempt.

"One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary." --Ayn Rand

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happyshub

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Re: how to reverse link list using recurtion

Jun 8th, 2005

•

Originally Posted by Dave Sinkula

Show an attempt.

Ohhh I am new to the forum and I was not knowing the rules :mrgreen: :p That I have to show attempt ...

Here is what I was trying to do ! :evil: :evil:

Without Recurtion :-)

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
struct node *p,*q,*r;
r=null;
p=head;
while(p)
{
    q=p->next;
    p->next=r;
    r=p;
    p=q;
}
head=p;
struct node *p,*q,*r;
r=null;
p=head;
while(p)
{
    q=p->next;
    p->next=r;
    r=p;
    p=q;
}
head=p;

With recurtion :

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
   list *tail;  
 
list *reverse (list *head)  
{  
  if (head->next == NULL)  
  {  
    tail = head;  
    return;  
  }else{  
    reverse (head->next);  
    head->next->next = head;  
    head->next = NULL;  
  }  
}
   list *tail;  
 
list *reverse (list *head)  
{  
  if (head->next == NULL)  
  {  
    tail = head;  
    return;  
  }else{  
    reverse (head->next);  
    head->next->next = head;  
    head->next = NULL;  
  }  
}

<< moderator edit: added [code][/code] tags >>

In general can we reverse link list using REFERERCNCE to pointer as function parameter ....

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Dogtree

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Re: how to reverse link list using recurtion

Jun 8th, 2005

You're on the right track. Try incorporating a temporary link into your function rather than trying to work just with head and its next links.

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Re: how to reverse link list using recurtion

Jun 8th, 2005

•

Originally Posted by Dogtree

You're on the right track. Try incorporating a temporary link into your function rather than trying to work just with head and its next links.

Temperary variable to be passed in recursive function :evil: ??

temparary variable are temparary to scope of function and in recursive function we use global variable sort of things :rolleyes:

In general we can use static pointer but then toomit does not workk

CAN ANYONE HELP ME ITS URGENT :cry: :cry:

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Dogtree

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Re: how to reverse link list using recurtion

Jun 8th, 2005

>> Temperary variable to be passed in recursive function
No.

>> temparary variable are temparary to scope of function
Yea.

>> and in recursive function we use global variable sort of things
What are you babbling about? It's possible and perfectly reasonable to use a non-static local variable in a recursive function. This function doesn't need a static variable or a global variable. Here's your current function:

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
list *reverse (list *head)
{
  if (head->next == NULL)
  {
    tail = head;
    return;
  }else{
    reverse (head->next);
    head->next->next = head;
    head->next = NULL;
  }
}
list *reverse (list *head)
{
  if (head->next == NULL)
  {
    tail = head;
    return;
  }else{
    reverse (head->next);
    head->next->next = head;
    head->next = NULL;
  }
}

Here's my modification using a local temporary:

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
link *reverse_list(link *head)
{
  link *temp;
 
  if (head->next == 0) temp = head;
  else {
    temp = reverse_list(head->next);
    head->next->next = head;
    head->next = 0;
  }
 
  return temp;
}
link *reverse_list(link *head)
{
  link *temp;

  if (head->next == 0) temp = head;
  else {
    temp = reverse_list(head->next);
    head->next->next = head;
    head->next = 0;
  }

  return temp;
}

The algorithm is identical, but my function is completely self-contained and works properly whereas yours would have unnecessary coupling with that global variable if you kept following the same line of thinking.