Linked list

This is a discussion on Linked list within the C++ Programming forums, part of the General Programming Boards category; I have this sort, can someone tell me why the code it not sorted correctly. Here is an example run ...

  1. #1
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    Linked list

    I have this sort, can someone tell me why the code it not sorted correctly. Here is an example run of it.

    Enter coefficient and exponent (0 0 to stop):9 8
    Enter coefficient and exponent (0 0 to stop):3 10
    Enter coefficient and exponent (0 0 to stop):6 2
    Enter coefficient and exponent (0 0 to stop):10 44
    Enter coefficient and exponent (0 0 to stop):9 120
    Enter coefficient and exponent (0 0 to stop):0 0
    DEBUG: before sort
    9 8 3 10 6 2 10 44 9 120

    3 10 10 44 9 120 9 8 6 21
    DEBUG: After sort

    It should be 9 120 10 44 3 10 9 8 6 2

    counter is the size of the list.
    Code:
    void LList::sort() {
    listNode *temp;
    temp = head;  
      int j;
    for(j = 0; j < counter; j++)  {    
         
      while(temp->next != NULL) {
         if(temp->expo < temp->next->expo) {
             int tempInt, tempInt2;
             tempInt = temp->next->expo;
             tempInt2 = temp->next->coef;
             temp->next->expo = temp->expo;
             temp->next->coef = temp->coef;
             temp->expo = tempInt;
             temp->coef = tempInt2;
         } else {
            temp = temp->next;
         }
      } //end while
    } // end for
    
    } // end function
    
    This is the class decleration of the list
    
    class listNode {
     public:
      int coef;
      int expo;
      listNode *next;
    
    };
    Any help would be great thanks.


    Code tagged by Hammer.

  2. #2
    End Of Line Hammer's Avatar
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    Please use Code Tags when posting code.
    When all else fails, read the instructions.
    If you're posting code, use code tags: [code] /* insert code here */ [/code]

  3. #3
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    You say you wanted it to be sorted right. How sorted least to greastest. You say 3 10 10 44 9 120 9 8 6 21 but thats not in order .
    It should be 3 6 8 9 9 10 10 21 44 120.
    Maybe try a bubble sort?

  4. #4
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    try moving the line

    temp = head;

    after the for() loop and before the while() loop so temp starts at head each time the for loop is run, rather than just once as it is.

  5. #5
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    It does not look like you are sorting your elements. Instead you are copying the data over existing elements.

    You need 5 pointers in a standard linked list. head, end,current,next,prev. head, end and current are usually in a base class. The next and prev are in a derived class with your other class specific data.

    You should never be referencing the elements of your pointers, other than next and prev.

    if( current->exp < next->exp)
    {
    //Insert the temp element in the list before next and update the pointers.
    current->next=next;
    current->prev=next->prev;
    next->prev=current;
    }
    Last edited by bonkey; 11-01-2002 at 12:48 PM.
    Best Regards,

    Bonkey

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