search a number in linklist

Question

4.00/5 (1 vote)

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There is a sample:

// searchlist.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include<iostream>
using namespace std;

class node
{
	friend class linklist ;
	int data ;
	node *next ;
};

class linklist
{
public:
	linklist();
	void insert();
	void serach();
private:
	node *last;
};

 linklist::linklist()
{
	last = NULL ;
 }


 void linklist::insert()
{
	node *p = new node();
	p-> data = NULL ;

		if(last == NULL)
		{
			last = p;
		}
		else
		{
			p -> next = last -> next  ;
			last -> next = p ;
		}
	
	
}
void linklist ::serach()
{
	int n ;
	cout << "Enter the place of the number that you want ?" << endl ;
	cin >> n ;

	int m ;
	cout << "plz enter the numbers of numbers :" << endl ;
	cin >> m ;

	node *cur = last ;
	cur -> next = NULL ;
	while(cur!=NULL )
	{
		for(int i = m ;  n > 0 ; i-- )
		{
			cout << cur->next << "yay" ;
			
		}
	}
}


int main()
{
	int m , o ;
	cout << "plz enter the numbers of numbers :" << endl ;
	cin >> m ;
	cout << "plz enter the numbers : " << endl ;
	for(int i = 0 ; i < m ; i++ )
	cin>>o;
	linklist h;
	h.insert();
	h.serach();

	return 0;
}

1 2 3 4 5 6 i want to find the second number from the last .and the answer that my program given to me is wrong

Posted 5-Apr-11 21:08pm

yay hello

Updated 5-Apr-11 21:46pm

v3

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3 solutions

Solution 2

Before discussing any problems with your code: remove all I/O from the class linklist and modify its interface accordingly, otherwise there is no subject for discussion. You're not developing pure list class but something that cannot be used due to this I/O. Ever heard of separation of concerns?

—SA

Posted 5-Apr-11 21:33pm

Sergey Alexandrovich Kryukov

Comments

CPallini 6-Apr-11 4:36am

You know, I agree with you (have my 5). However, here we've even more basic technical gaps to fill, in my opinion.

Sergey Alexandrovich Kryukov 6-Apr-11 15:46pm

Thank you very much.
You are absolutely right about "even more basic technical gaps to fill". But -- are we able to fill then in the CodeProject format? Hardly, I'm afraid, so...
I simply used the principle "I don't have to eat the whole egg to tell its bad". Can I?

Thanks again.
--SA

CPallini 6-Apr-11 16:10pm

Yes, you can.

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OriginalGriff · Accepted Answer · 2011-04-05T21:24:00

Solution 1

I'm not surprised.
There is so much wrong with your program. One example that leaps out as I am typing this:

for(int i = m ;  n > 0 ; i-- )
{
    cout << cur->next << "yay" ;
    exit(0);
}

I am so glad that the loop is irrelevant - you exit the application on the first iteration - but if you didn't, what changes "n"? What moves "cur" to stop it showing the same line, over and over, and over?
That this is inside another loop that can't end either hardly seems mentioning.

Go back to the beginning. Check your code, and run it through the debugger. I think you have to look at everything you have done, and see if it works, and why it works, before you start moving on.

Posted 5-Apr-11 21:24pm

OriginalGriff

Comments

Sergey Alexandrovich Kryukov 6-Apr-11 3:35am

The code is so helpless, so pointing out the first non-fixable problem is quite enough, my 5.
I've done something similar, please see.

By the way, it happens second time here. Last time I failed to convince the patient to remove I/O from the similar class. It it is not apparent why, I don't know what to talk about...
--SA

OriginalGriff 6-Apr-11 3:58am

Hi SA! Maybe it's a little early for him to think about code reuse: would you want to reuse this code? :laugh:
Congratulations on reaching the top of both leaderboards BTW - I said you would!

Sergey Alexandrovich Kryukov 6-Apr-11 4:06am

Thank you.
I was thinking: what to answer you about re-use? Looks like you're right, to early, but... something's wrong.
You see, thinking about real reuse may be to earlier. But this is not lack of reuse, this is anti-reuse! Do you see the difference?
--SA

OriginalGriff 6-Apr-11 4:25am

Oh I get it, trust me! I think I could re-use this code, but only in the "Hall of Shame" - which would be too cruel on beginners :laugh:

Sergey Alexandrovich Kryukov 6-Apr-11 16:15pm

Of course I trust you on that. As to the rest... not that I can help it. See also my comment to the CPallini's comment on my Answer... :-)
Thank you.
--SA

CPallini · Accepted Answer · 2011-04-05T21:42:00

Try this:
(please note you forgot the cleanup, i.e. deleting nodes in the list destructor, as C++ developer you HAVE TO provide cleanup)

C++

#include "stdafx.h"
#include<iostream>
using namespace std;
class node
{
    friend class linklist ;
    int data ;
    node *next ;
};
class linklist
{
public:
    linklist();
  ~linklist();
    void insert();
    void serach();
private:
    node *last;
};
linklist::linklist()
{
    last = NULL ;
 }
// cleanup
linklist::~linklist()
{
  node * pcur, * pnext;
  pcur = last;
  while ( pcur )
  {
    pnext = pcur->next;
    delete pcur;
    pcur = pnext;
  }
}

void linklist::insert()
{
  node *p;

    int m ;
    cout << "plz enter the numbers of numbers :" << endl ;
    cin >> m ;

    cout << "plz enter the numbers : " << endl ;
  for(int i = 0 ; i < m ; i++)
    {
    p = new node();
    p->next = NULL;
        cin >> p->data ;
    if(last == NULL)
      {
          last = p;
      }
      else
      {
          p->next = last->next  ;
          last->next = p ;
      }
    }
}
void linklist ::serach()
{
    int n ;
    cout << "Enter the place of the number that you want ?" << endl ;
    cin >> n ;
    node *cur = last ;
    while( n-- )
    {
        if ( cur == NULL) return;
    cur = cur->next;
    }
  cout << "found: " << cur->data << endl;
}

int main()
{
    linklist m;
    m.insert();
    m.serach();
    return 0;
}