Linked List with Char Array problem

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Linked List with Char Array problem

 
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  #1
Apr 1st, 2009
Hey All,
I'm having this weird issue and I'm not sure what to do. In the main function when I put one letter it'll work, once I put a string of letters it doesn't work. I've tried an assortment of stuff and I dunno what to do anymore.

This is the code that works when I put one letter in. Right now in the main it has "first", "second", and "third" and I get error C2664: cannot convert parameter 1 from 'const char[6]' to 'char'.

Thanks in advanced.

c++ Syntax (Toggle Plain Text) 
  1. #include <iostream>
  2. #include <cstring>
  3. using namespace std;
  4.  
  5. class CharNode
  6. {
  7. public:
  8.     CharNode(){}
  9.     CharNode(char d, CharNode *lPtr)
  10.         : data(d), linkPtr(lPtr){}
  11.     CharNode *getLink() const {return linkPtr;}
  12.     char getData() const {return data;}
  13.     void setData(char d) {data=d;}
  14.     void setLink(CharNode *lPtr) {linkPtr = lPtr;}
  15.     void headInsert(CharNode* &head, char d);
  16.     void deleteTail (CharNode *before);
  17.     void printAll();
  18. private:
  19.     char data;
  20.     CharNode *linkPtr;
  21. };
  22.  
  23. void CharNode::headInsert(CharNode* &head, char d)
  24. {
  25.     head = new CharNode(d, head);
  26. }
  27.  
  28. void CharNode::deleteTail(CharNode *head)
  29. {
  30.     CharNode *discard, *tail;
  31.     tail = head;
  32.  
  33.     // move tail to the last but one node
  34.  
  35.     while ((tail->getLink())->getLink() != NULL)
  36.         tail = tail -> getLink();
  37.  
  38.     tail -> setLink(NULL);
  39.     discard = tail->getLink();
  40.     delete discard;
  41. }
  42.  
  43. void CharNode::printAll()
  44. {
  45.     if (this == NULL)
  46.         cout << "Empty list\n";
  47.  
  48.     else
  49.     {
  50.         int i = 1;
  51.         CharNode *tempPtr = this;
  52.         cout << "The linked list is: \n";
  53.         while (tempPtr != NULL)
  54.         {
  55.             cout << "Object " << i++ << ": " << tempPtr->getData() << endl;
  56.             tempPtr = tempPtr->getLink();
  57.         }
  58.     }
  59. }
  60.  
  61. int main()
  62. {
  63.     CharNode *head = new CharNode("First", NULL);
  64.     head->headInsert(head,"Second");
  65.     head->headInsert(head,"Third");
  66.     head->printAll();
  67.     delete head;
  68.     head=NULL;
  69.     head->printAll();
  70.  
  71.     system("PAUSE");
  72.     return 0;
  73. }
Last edited by Drifter666; Apr 1st, 2009 at 10:39 am.
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Re: Linked List with Char Array problem

 
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  #2
Apr 1st, 2009
Your CharNode contains member "char data;" and you're trying to assign a string "First" to that char. That isn't going to work because "First" is actually a pointer to a null terminated array of chars and you're trying to say: char = pointer to char.
If you want strings in your linked list you need to provide a different member type for the storage in the CharNode class.
This could be an STL string, a char* to memory you'll have to allocate yourself or, the simplest solution is a fixed length char array (if you do this make sure you copy all chars to it, don't just try and copy the pointer).
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Re: Linked List with Char Array problem

 
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  #3
Apr 1st, 2009
Thanks MrSpigot. Makes sense.


Ok. I made them pointers. The program runs but it only prints out the first letter of each string. So I tried to make the headinsert function like this:

head = new CharNode((strlen(d)+1), head);

but that doesn't work either.

I'm just looking for an easy way out right now. Let's say the fixed character length is 20. But when I try to implement I get tons more errors. I'm not familiar with linked lists at all, so this is all kinda new to me.

Again, thanks in advanced.

c++ Syntax (Toggle Plain Text) 
  1. #include <iostream>
  2. #include <cstring>
  3. using namespace std;
  4.  
  5. class CharNode
  6. {
  7. public:
  8.     CharNode(){}
  9.     CharNode(char *d, CharNode *lPtr)
  10.         : data(d), linkPtr(lPtr){}
  11.     CharNode *getLink() const {return linkPtr;}
  12.     char getData() const {return *data;}
  13.     void setData(char *d) {data=d;}
  14.     void setLink(CharNode *lPtr) {linkPtr = lPtr;}
  15.     void headInsert(CharNode* &head, char *d);
  16.     void deleteTail (CharNode *before);
  17.     void printAll();
  18. private:
  19.     char *data;
  20.     CharNode *linkPtr;
  21. };
  22.  
  23. void CharNode::headInsert(CharNode* &head, char *d)
  24. {
  25.     head = new CharNode(d, head);
  26. }
  27.  
  28. void CharNode::deleteTail(CharNode *head)
  29. {
  30.     CharNode *discard, *tail;
  31.     tail = head;
  32.  
  33.     // move tail to the last but one node
  34.  
  35.     while ((tail->getLink())->getLink() != NULL)
  36.         tail = tail -> getLink();
  37.  
  38.     tail -> setLink(NULL);
  39.     discard = tail->getLink();
  40.     delete discard;
  41. }
  42.  
  43. void CharNode::printAll()
  44. {
  45.     if (this == NULL)
  46.         cout << "Empty list\n";
  47.  
  48.     else
  49.     {
  50.         int i = 1;
  51.         CharNode *tempPtr = this;
  52.         cout << "The linked list is: \n";
  53.         while (tempPtr != NULL)
  54.         {
  55.             cout << "Object " << i++ << ": " << tempPtr->getData() << endl;
  56.             tempPtr = tempPtr->getLink();
  57.         }
  58.     }
  59. }
  60.  
  61. int main()
  62. {
  63.     CharNode *head = new CharNode("First", NULL);
  64.     head->headInsert(head,"Second");
  65.     head->headInsert(head,"Third");
  66.     head->printAll();
  67.     delete head;
  68.     head=NULL;
  69.     head->printAll();
  70.  
  71.     system("PAUSE");
  72.     return 0;
  73. }
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Re: Linked List with Char Array problem

 
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  #4
Apr 1st, 2009
C++ Syntax (Toggle Plain Text) 
  1. void CharNode::headInsert(CharNode* &head, char *d)
  2. {    
  3.     head = new CharNode(d, head);
  4. }

What the above says is create a new list every time you insert a new item. T'm almost positive that isn't what you want. I strongly recommend you have two classes, not one. One to define a node that will be inserted in a list, and the other to define the list itself. The node class will have one or more data member variables and one (or more if you want more than a singly linked list) pointer variable(s) to the node type itself. When you want to insert a new node into a list you declare memory for a new node, not a new list. Each list should have a node pointer to keep track of the first node in the list which is often called head.
Klatu Barada Nikto
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Re: Linked List with Char Array problem

 
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  #5
Apr 1st, 2009
Thanks Lerner. I will take that approach next time.

I messed with the code again and with a little help from a local friend, we fixed it finally. Something I overlooked in the class definition. Thanks for your help guys.

here's the final code in case someone else needs to take a look.

c++ Syntax (Toggle Plain Text) 
  1. #include <iostream>
  2. #include <cstring>
  3. using namespace std;
  4.  
  5. class CharNode
  6.  
  7. {
  8. public:
  9.     CharNode(){}
  10.     CharNode(char d[], CharNode *lPtr)
  11.         : linkPtr(lPtr)
  12.         {
  13.                 strcpy(data,d);
  14.         }
  15.     CharNode *getLink() const {return linkPtr;}
  16.     char *getData() {return data;}
  17.     void setLink(CharNode *lPtr) {linkPtr = lPtr;}
  18.     void headInsert(CharNode* &head, char *d);
  19.     void deleteTail (CharNode *before);
  20.     void printAll();
  21. private:
  22.     char data[20];
  23.     CharNode *linkPtr;
  24. };
  25.  
  26. void CharNode::headInsert(CharNode* &head, char *d)
  27. {
  28.     head = new CharNode(d, head);
  29. }
  30.  
  31. void CharNode::deleteTail(CharNode *head)
  32. {
  33.     CharNode *discard, *tail;
  34.     tail = head;
  35.  
  36.     // move tail to the last but one node
  37.  
  38.     while ((tail->getLink())->getLink() != NULL)
  39.         tail = tail -> getLink();
  40.  
  41.     tail -> setLink(NULL);
  42.     discard = tail->getLink();
  43.     delete discard;
  44. }
  45.  
  46. void CharNode::printAll()
  47. {
  48.     if (this == NULL)
  49.         cout << "Empty list\n";
  50.  
  51.     else
  52.     {
  53.         int i = 1;
  54.         CharNode *tempPtr = this;
  55.         cout << "The list is: ";
  56.         while (tempPtr != NULL)
  57.         {
  58.             cout << tempPtr->getData() << " ";
  59.             tempPtr = tempPtr->getLink();
  60.         }
  61.     }
  62. }
  63.  
  64. int main()
  65. {
  66.     CharNode *head = new CharNode("First", NULL);
  67.     head->headInsert(head,"Second");
  68.     head->headInsert(head,"Third");
  69.     head->printAll();
  70.     cout << endl;
  71.     delete head;
  72.     head=NULL;
  73.     head->printAll();
  74.  
  75.     system("PAUSE");
  76.     return 0;
  77. }
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