Program Help. Constructors, String, Linked List

[ShvpDjzh]

Help with voidPrint()

[SECMoG1T]

Hi

 
   struct Node
    {
       char acid;
       Node *next; 
     }

DNA(string dna); // initalizes the strand to the string  
  /// can work if you may use a loop and insert it's char values in new nodes added to strand.since your
  /// nodes take a single char each. 

 void print (int begin,  int end) const; // I have no idea if it will work because a linked list isn't indexed
 
 
/*You might check this one out*/
  
 void print (const Node *&mystrand) ///passes by reference
         {
              Node *temp=mystrand; ///copy mystrand into a temporary pointer. 
              /// this will apply only if you strand ends with a nullptr value on the last pointer. 
               while (temp!=nullptr)
                {
                   cout <<temp-> acid; 
                   temp=temp-> next; /// moves temp to the next node;
                }
          }


// do something similar here
Dna substr (int begin, int end) const; 

             

[SECMoG1T]

Oh sorry I dint see this legal input as (n,m) where (0<=n< m). n am puzzled right now.

[ShvpDjzh]

Thank You Andy but the void print function must stay like that for the program, instructed by the instructor.


How would you insert char values in new nodes?

[ShvpDjzh]

@andy1992 its very fustrating

[SECMoG1T]

Okay tell me what are int begin, int end i'll help , are they indexes are they values? i need a clue on that

[ShvpDjzh]

It wasn't given but in the print function it shows

    void print(int begin, int end) const; 
    
     // prints the strand from begin to end
     //the first position is 0
     //output gattaca.print(1,3) is att) 

So would that make them indexes?

Where (1,3) is inputted with gattaca.print(1,3) it would print out att. So I was guessing it was (begin, end) perhaps. But wouldn't we have to format the string into a char array then initialize the char array into print with begin and end?

[ShvpDjzh]

@andy1992, first wouldn't we need to do the this function first:

DNA(string dna) 
{

}

Where it would initialize the string to char array and store them in the Nodes. I'm confused on doing that.

[SECMoG1T]

okay its pretty simple as you have your struct as node hence all it's members are public

/// example
  struct Node
      { 
          char acid;
           Node *next; 
       } 
     

 DNA::DNA(string dna)
 {
    if (dna.size ()==0){cout<<"empty string" ;}/// exit
  
   strand-> acid=dna [0];
   strand-> next= nullptr; 
   ++length; 
   /// if string size is greater than one continue adding

   int index=1;
   Node *back=strand-> next;

   while(index <dna.size ())
       {
          back=new Node; 
          back-> acid=dna [index]; ++length; 
          back-> next= nullptr; 
          back=back-> next;//// moves back to the last pointer
          ++index; 
        }
 }

[ShvpDjzh]

Ok that makes sense. Now the next step would be initializing the dna[index] with begin and end correct? and that would be within the print function.

Now a question for the example you provided should we include a cin to enter a string or no?

[SECMoG1T]

Hi note that above is just a constructor , you'll have to make a function that add a single node for
efficiency , bearing in mind that the user might not have the intial dna as a strand and will add base after base

Okay if your print function must take int begin, int end then you can use pointer arithmetics though I don't know if they will work fine for linked lists

void print (int begin,  int end) /// am not sure on these coz am not sure how the nodes are in memory
  {                                                 /// if they are contiguous and if pointer arithmetic apply to 'em
     Node *temp=strand+begin; /// just try
     Node *myend=strand+end;
  
     while (temp!=myend)
          {
             cout <<temp-> acid; 
             temp=temp-> next;/// move to next node
          }
   }

[SECMoG1T]

Am more casual method

void print(int begin,  int end)
 {
     Node* start;
     Node* myend; 
     Node* temp=strand; 

    Int i=1;
    while (i <begin)
            {
               temp=temp-> next;++i; 
            }
      
          start=temp;  temp=strand; i=1;
   
      while (i <end)
            {
                temp=temp-> next; ++i; 
             }

          myend=temp;
       while (start!=myend)
            {
                cout <<start-> acid; 
                start=start-> next;
             }
    
  }

[ShvpDjzh]

@andy1992, ok I am going to try to work with what you gave for the print function. Are we able to chat on here privately?

[SECMoG1T]

try them hope they work btw this is a public forum .

[ShvpDjzh]

No it does not work, so for the

DNA(string dna)
{
 for (int i = 0; i < dna.length(); i++)
     add2Last(dna[i]);
}

But now we would have to create an add2Last()

That confuses me. @andy1992

[SECMoG1T]

add2last () // is a function you seem to have defined

You add a single base to the strand

void add2last (char b)
 {
    ///if strand is empty set b to to its acid
    if (length==0)
       {
          strand-> base=b;   ++length; 
          strand-> next=nullptr; 
        }
     
    else
     {
         Node *temp=strand-> next;
         
         while (temp!=nullptr)  /// loop exit when next pointer is nullptr i.e. end of strand
                temp=temp-> next;
               
              Node *end=new Node;
              end-> acid=b;
              end-> next=nullptr; 
              temp=end; ++length; 
     }
}
 

What is the error on print function