//Author:	R.P. Patillo


// File: gradelnklist.cpp.  Contents: C++ source code for dynamic memory
// allocation implementation of a list of grades.  Each node in the list 
// contains a grade and the occurrence count for that grade.
// The grades are stored in ascending order.
//

#include "gradelnklist.h"
#include <iostream>
#include <iomanip>
using namespace std;

// ---------- general list members first ----------

// --------------------------------------------------------------------
// GradeList constructor -  initializes a list to empty
// --------------------------------------------------------------------
// Accepts:  nothing
// Returns:  nothing
// --------------------------------------------------------------------

GradeList::GradeList()
{
head = NULL;
}

// --------------------------------------------------------------------
// GradeList destructor - deletes all nodes in list
// --------------------------------------------------------------------
// Accepts:  nothing
// Returns:  nothing
// --------------------------------------------------------------------

GradeList::~GradeList()
{
NodeType* tmp;    // temp ptr for deleting nodes

while (head != NULL)    // destroy nodes one by one
{
    tmp = head;
    head = head->next;
    delete tmp;
}
}

// --------------------------------------------------------------------
// IsEmpty - test for empty list
// --------------------------------------------------------------------
// Accepts:  nothing
// Returns:  true if the list is empty, false otherwise.
// --------------------------------------------------------------------

bool GradeList::IsEmpty(void)
{
return (head == NULL);
}

// --------------------------------------------------------------------
// IsFull - test for full list
// --------------------------------------------------------------------
// Accepts:  nothing
// Returns:  false always, because, within the bounds of memory size,
//           the list never fills!
// --------------------------------------------------------------------

bool GradeList::IsFull()
{
return false;
}

// -------------------------------------------------------------------
// Display - prints the grades in the list, one grade per line
// -------------------------------------------------------------------
// Accepts:  nothing
// Returns:  nothing
// -------------------------------------------------------------------

void GradeList::Display()
{
NodeType* tmp = head;   // temp ptr for traversing list

if (IsEmpty())
    cout << "\nThere are no grades\n\n";
else
{
    cout << "\nGrades    Num of Each \n\n";
    while (tmp != NULL)
    {
        cout << setw(4) << tmp->grade << setw(14) << tmp->count << "\n";
        tmp = tmp->next;
    }
}

}

// -------------------------------------------------------------------
// Function to insert a new grade into the list in ascending order
// -------------------------------------------------------------------
// Accepts:  the new grade
// Returns:  nothing
// -------------------------------------------------------------------

void GradeList::InsertGrade(int newgrade)
{
NodeType* curr = head;   // temp ptr for traversing list
NodeType* prev = NULL;   // temp ptr for traversing list
NodeType* tmp;           // temp ptr to create new node

while (curr != NULL && curr->grade < newgrade)  // find place to insert
{
    prev = curr;
    curr = curr->next;
}

if (curr != NULL && curr->grade == newgrade)    // grade already here ...
    curr->count++;                              // ... simply inc. count
else
    if (prev == NULL)    // empty list or insert at beginning
    {
        tmp = new NodeType;
        tmp->grade = newgrade;
	tmp->count = 1;
	tmp->next = head;
	head = tmp;
    }
    else                 // insert in middle or at end
    {
	tmp = new NodeType;
	tmp->grade = newgrade;
	tmp->count = 1;
	tmp->next = curr;
        prev->next = tmp;
    }
}

// -------------------------------------------------------------------
// Function to delete the indicated grade from the list
// -------------------------------------------------------------------
// Accepts:  grade to delete
// Returns:  nothing
// -------------------------------------------------------------------

void GradeList::DeleteGrade(int delgrade)
{
    NodeType* curr = head;
    NodeType* prev = NULL;
    NodeType* tmp;

    while (curr != NULL && curr->grade < delgrade)  		//Locates desired grade for deletion.
    {
    	prev = curr;
    	curr = curr->next;
    }

    if (curr != NULL && curr->grade == delgrade)		//Lowers grade count or deletes desired grade depending on location in
    { 								// linked list.
   	curr->count--;

        if (curr->count == 0)
	{
	    if(prev == NULL)
	    {
		head = curr->next;
    		delete curr;
	    }
	    
	    else
	    {
		tmp = curr->next;
		prev->next = tmp;
	    	delete curr;

 	    }
	}  
    }
}

// -------------------------------------------------------------------
// Function to calculate the average of the grades in the list
// -------------------------------------------------------------------
// Accepts:  nothing
// Returns:  the average (0 if list is empty)
// -------------------------------------------------------------------

float GradeList::CalculateAvg()
{
    NodeType* curr = head;
    NodeType* prev = NULL;

    float totalsum = 0.0;
    int totalcount = 0;

    while (curr != NULL)				// The while loop continues to calculate total sum and total count
    {							// until curr equals NULL.
	totalsum+= (curr->grade * curr->count);
	totalcount+= curr->count;
	prev = curr;
	curr = curr->next;	
    }

    if (totalcount!=0)
 	return totalsum/totalcount;
    else
	return 0;

}

// -------------------------------------------------------------------
// DropLowestGrade - drops the lowest grade in the list, does nothing
//                   if list is empty
// -------------------------------------------------------------------
// Accepts:  nothing
// Returns:  nothing
// -------------------------------------------------------------------

void GradeList::DropLowestGrade()
{
    NodeType* tmp = head;

    if(head!=NULL)			// if head doesn't point to NULL then drops grade count by 1 or deletes it
    {
	if (tmp->count != 1)
	    tmp->count--;

    	else
	{
            head = tmp->next;
            delete tmp;
	}
    }
}
     
// -------------------------------------------------------------------
// HowManyofGrade -  returns how many times this grade is in the list
// -------------------------------------------------------------------
// Accepts:  the grade to look for
// Returns:  the number of times the grade is in the list
// -------------------------------------------------------------------

int GradeList::HowManyofGrade (int grade)
{
    NodeType* curr = head;
    NodeType* prev = NULL;

    if (head == NULL)		// returns zero if head point to NULL
        return 0;

    while (curr!=NULL && curr->grade < grade)	// locates grade if present
    {
	prev = curr;
	curr = curr->next;
    }

    if (grade == curr->grade)			// returns curr grade if equal to grade
	return curr->count;

    else
	return 0;				// returns zero if grade is not present
}