#include "stdstuff.h"
#include "List.h"

// the destructor destroys the list one node at a time, starting from the head
List::~List () {

  Node *t;
  while (head != NULL) {
    t = head; head = head -> next; delete t;
  }

}


// prints the list to cout one node at a time, starting with the head
void List::outputList () const {
  
  Node *c = head;
  int i = 0;

  cout << "The list contains:" << endl;

  while (c != NULL) {
    cout << "  " << c -> data;
    if (++i == 10) {
      cout << endl; i = 0;
    }
    c = c -> next;
  }
  if (i != 0) cout << endl;

}


// inserts a node into the list at the head of the list
void List::insert (int data) {

  head = new Node (data, head);

}


// Method "countOddValues" returns the number of nodes in the list containing odd values.
// Note that "containing" refers to the *contents* of the node, not its position in the list.
// If the list contains no odd values, it returns 0.
int List::countOddValues() const {

   int count = 0;

   for (Node* c = head; c!=NULL; c=c->next) { // check every node
      if (c->data%2!=0)  // if it's odd, count it
         count++;
   }

   return count; 

}


// Method "deleteValuesMultThree" deletes every node containing
// a value that is an exact multiple of 3 (i.e. ..., -9, -6, -3, 0, 3, 6, ...). 
// If the list contains no values that are multiples of 3, it has no effect.
void List::deleteValuesMultThree() {

   Node *c = head, *p = NULL, *temp;

   while (c!=NULL) {

      if (c->data%3==0) { // node contains a multiple of 3, so delete it and move to next node

         if (p==NULL) // if deleting first node
            head = c->next; // head now points to 2nd
         else
            p->next = c->next;  // otherwise previous node points to next node

         temp = c; 
         c = c->next; // move on to next node
         delete temp; // and delete the one containing a multiple of 3

      } else { // just move on to next node

         p = c;      
         c = c->next;

      }

   }

}