List of nodes

This is a discussion on List of nodes within the C++ Programming forums, part of the General Programming Boards category; I have a struct as follows Code: struct node{ int x; int y; node *next_nodex; } node r_table[360]; These are ...

  1. #1
    Registered User
    Join Date
    Jan 2003
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    37

    List of nodes

    I have a struct as follows

    Code:
    struct node{
      int x;
      int y;
      node *next_nodex;
    }
    
    node r_table[360];
    These are delcared globally. I know this is bad but it does initilise everything if declared globally.

    I have a function which decides which element in the array.

    How would I get to the last element in one of the lists. Is it something like this.

    Code:
    node *tmp_ptr;
    
            tmp_ptr = &(r_table[table_indx]);
    
            // Goto to end of list
            while (tmp_ptr->next_node != NULL)
              tmp_ptr = tmp_ptr->next_node;
    
            // Add new node
            tmp_ptr->next_node = new(node);
    
            // Step into new node
            tmp_ptr = tmp_ptr->next_node;
    
            tmp_ptr->x = x_anchor - col;
            tmp_ptr->y = y_anchor - row;
            tmp_ptr->next_node = NULL;
    Thanks

  2. #2
    Registered User Codeplug's Avatar
    Join Date
    Mar 2003
    Posts
    4,671
    Looks good - but here is an optimization:
    Code:
    typedef struct _node
    {
        int x;
        int y;
        _node *next_nodex;
    
        _node() : next_nodex(NULL) {}
    } node_t;
    
    typedef struct _node_array_elem
    {
        node_t *first,*last;
    
        _node_array_elem() : first(NULL),last(NULL) {}
    } node_array_elem_t;
    
    node_array_elem_t r_table[360];
    
    ...
    
        node_array_elem_t *tmp_ptr;
        tmp_ptr = r_table + table_indx;
    
        node_t *new_node = new(node_t);
    
        // Add new node
        if (tmp_ptr->last != NULL)
        {
            tmp_ptr->last->next_nodex = new_node;
            tmp_ptr->last = new_node;
        }
        else
        {
            tmp_ptr->last = new_node;
            tmp_ptr->first = new_node;
        }
    
        new_node->x = x_anchor - col;
        new_node->y = y_anchor - row;
    If you are using "new", then you must be using C++, so you can also use constructors to perform initialization (which also means the typedef's are really necessary, but I like em). And then the optimization part: why traverse to the end of the list every time if you can just remember where the end is?

    gg

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