Linked lists...need help with a little something

[Todd88]

I have written a code that takes data from a text file and inputs it into a linked lists then allows the user to manipulate the data. What I have in the file is a name, id, weight, and height. The program currently calculates the BMI for each member and prints this out too. The only thing I allow the user to manipulate is the weight for a certain member. What I need is to have the output display the CURRENT weight and the INITIAL weight. I get it to display the current weight after the changes but not the initial. Thanks in advance.

Here is my code:

#include <iostream>
#include <iomanip>
#include <fstream>
#include <cmath>
#include <string>

using namespace std;

struct memberType
{
       string name;
       int id;
       double height;
       double weight;
       double bmi;
};

typedef memberType infoType;

struct nodeType
{
     infoType info;
     nodeType  *link;
};

double calcBmi (double weight, double height);
void printOne (infoType x);memberType getOne(ifstream& inFile);

void print (nodeType *list);
void printHealthy (nodeType *list);
void printOut (nodeType *list, ofstream& outFile);
nodeType * addToList (infoType a, nodeType *list);
void printOneOut (infoType one, ofstream& outFile);
int search (int id, nodeType *list);
nodeType * change (nodeType *list, double i, double& w);

int main ()
{
    nodeType *healthy = NULL;
    int id;
    char n;
    infoType a;
    string name, inputFile;
    double height, weight, bmi;
    

    ifstream inFile;
    ofstream outFile;
     
     cout << "Enter the name of the input file: ";
     cin >> inputFile;
     cout << endl << endl;
      
     inFile.open(inputFile.c_str());
     outFile.open("members.txt");
     
     if(!inFile) 
     {
         cout << "Invalid file name" << endl;
         system("pause");
         return 1;
         }

    a = getOne (inFile);

    while (inFile)
    {
        healthy = addToList (a, healthy);
        a = getOne (inFile);
    }
   
    cout << "__________________________________________________________________"
         << "______\n";
    cout << "____________________________|ENTIRE LIST|_________________________"
         << "______" << endl;
    cout << left << setw(17) << "Name" 
         << left << setw(14) << "ID" 
         << left << setw(20) << "Height" 
         << left << setw(18) << "Weight"
         << right << "BMI" << endl;
    cout << "__________________________________________________________________"
         << "______\n";
    print (healthy);

    cout << "__________________________________________________________________"
         << "______\n";
    cout << "___________________________|HEALTHY PEOPLE|_______________________"
         << "______" << endl;
    cout << left << setw(17) << "Name" 
         << left << setw(14) << "ID" 
         << left << setw(20) << "Height" 
         << left << setw(18) << "Weight"
         << right << "BMI" << endl;
    cout << "__________________________________________________________________"
         << "______\n";
    printHealthy (healthy);

    cout << "Would you like to change a member's weight? (Y = Yes, N = No): ";
    cin >> n;
    cout << endl;

    while (n != 'n' || n != 'N')
    {
        if (n == 'y' || n == 'Y')
        {
        cout << "__________________________________________________________________"
             << "______\n";
        cout << "\nEnter the member's ID: " ;
        cin >> id;
        cout << endl;

        int y = search(id, healthy);

        if (y == -1)
            cout << "Person with id " << id << " not found.\n" << endl;
        else
        {
            cout << "Enter the new weight: " ;
            cin >> weight;
            cout << endl;

            change(healthy, y, weight);
            cout << "================================\n";
            cout << "= Weight change has been made. =\n";
            cout << "================================\n\n";
            cout << "________________________________________________________"
                 << "________________\n\n";
        }
        }
        else if (n == 'n' || n == 'N')
        {
              cout << "________________________________________________________"
                   << "________________\n";
              cout << "______________________________|NEW LIST|________________"
                   << "________________" << endl;
              cout << left << setw(17) << "Name" 
                   << left << setw(14) << "ID" 
                   << left << setw(20) << "Height" 
                   << left << setw(18) << "Weight"
                   << right << "BMI" << endl;
              cout << "________________________________________________________"
                   << "________________\n";
              print (healthy);

              cout << "________________________________________________________"
                   << "________________\n";
              cout << "____________________________|HEALTHY LIST|______________"
                   << "________________" << endl;
              cout << left << setw(17) << "Name" 
                   << left << setw(14) << "ID" 
                   << left << setw(20) << "Height" 
                   << left << setw(18) << "Weight"
                   << right << "BMI" << endl;
              cout << "________________________________________________________"
                   << "________________\n";
              printHealthy (healthy);

              outFile << "This file contains an output of the members.  Members" 
                      << " with a healthy BMI are listed first" << endl;
              outFile << " and those with a BMI below 18.5 are second followed "
                      << "by those with a BMI of 25 or higher.\n\n" << endl;
              outFile << "_____________________________________________________"
                      << "___________________\n";
              outFile << "____________________________|HEALTHY LIST|___________"
                      << "___________________" << endl;
              outFile << left << setw(17) << "Name" 
                      << left << setw(14) << "ID" 
                      << left << setw(20) << "Height" 
                      << left << setw(18) << "Weight"
                      << right << "BMI" << endl;
              outFile << "_____________________________________________________"
                      << "___________________\n";
              printOut (healthy, outFile);

              cout << "The final list was saved in \"Vrba.txt\" \n\n" ;

              break;
              }
        else
              cout << "Your selection of " << n << " is incorrect.\n\n";

        cout << "\nWould you like to change a member's weight?"
             << " (Y = Yes, N = No): ";
        cin >> n;
        cout << "\n\n";
       }

    system ("pause");
    return 0;
}

double calcBmi (double weight, double height)
{
   double bodyMassIndex;

   bodyMassIndex = 703 * weight / (pow (height,2));
   return bodyMassIndex;
}

memberType getOne (ifstream& inFile)
{
   memberType one;

   inFile >> one.name >> one.id >> one.height >> one.weight;

   one.bmi = calcBmi (one.weight, one.height);

   return one;
}

nodeType * addToList (infoType x, nodeType *list)
{
   nodeType *temp;

   temp = new nodeType;
   temp->info = x;
   temp->link=NULL;

   if (list == NULL)
   {
       list = temp;
       return list;
   }

   nodeType *current = list->link;
   nodeType *first = list;
   nodeType *prev = list;

   while (prev != NULL)
   {
        if (temp->info.id < first->info.id)
        {
            temp->link = first;
            return temp;
        }
        else if ((temp->info.id > first->info.id) && (first->link == NULL))
        {
            first->link = temp;
            return first;
        }
        else if (temp->info.id < current->info.id)
        {
            temp->link = current;
            prev->link = temp;
            list = first;
            return list;
        }

        else if (current->link == NULL)
        {
            current->link = temp;
            list = first;
            return list;
        }
       current = current->link;
       prev = prev->link;
   }

   list = temp;

    return list;
}

void print (nodeType *list)
{
     nodeType *current;
     current = list;

     while (current != NULL)
     {
       printOne ( current->info) ;
       cout << endl;
       current = current->link;
     }
     cout << endl;

}

void printHealthy (nodeType *list)
{
     nodeType *current;
     current = list;

     while (current != NULL)
     {
       if ((current->info.bmi >= 18.5) && (current->info.bmi <= 25))
       {
            printOne ( current->info) ;
            cout << endl;
       }
        current = current->link;
     }
     cout << endl;

}

void printOne (memberType one)
{
     one.bmi = calcBmi (one.weight, one.height);
     cout << fixed << showpoint << setprecision (1);
     cout << left << setw(8) << one.name << "\t" 
          << left << setw(8) << one.id << "\t" 
          << left << setw(8) << one.height << "\t" 
          << right << setw(8) << one.weight << "\t"
          << right << setw(8) << one.bmi;
}
int search (int id, nodeType *list)
{
    nodeType *current = list;

    for (int i=0; current != NULL; i++)
    {
        if (current->info.id == id)
            return i;
        current = current->link;
    }

    return -1;
}

nodeType * change (nodeType *list, double i, double& weight)
{
   nodeType *current = list;

   for (int a=0; a < i; a++)
      current = current->link;

    current->info.weight = weight;
}

void printOut (nodeType *list, ofstream& outFile)
{
     nodeType *current = list;

     while (current != NULL)
     {
       if ((current->info.bmi >= 18.5) && (current->info.bmi <= 25))
       {
            printOneOut ( current->info, outFile) ;
            outFile << endl;
       }
        current = current->link;
     }

     current = list;

     while (current != NULL)
     {
       if (current->info.bmi < 18.5)
       {
            printOneOut ( current->info, outFile) ;
            outFile << endl;
       }
        current = current->link;
     }

     current = list;

     while (current != NULL)
     {
       if (current->info.bmi > 25)
       {
            printOneOut ( current->info, outFile) ;
            outFile << endl;
       }
        current = current->link;
     }

     outFile << endl;
}

void printOneOut (infoType one, ofstream& outFile)
{
     one.bmi = calcBmi (one.weight, one.height);
     outFile << fixed << showpoint << setprecision(2);
     outFile << left << setw(8) << one.name << "\t" 
             << left << setw(8) << one.id << "\t" 
             << left << setw(8) << one.height << "\t" 
             << right << setw(8) << one.weight << "\t"
             << right << setw(8) << one.bmi;
}

[swoopy]

What you could do is to return the old weight from function change():

            old_weight = change(healthy, y, weight);

But the problem is you could only print the last old weight, which might not be the initial weight.

It sounds like you need to add a member to your class to store the initial weight, and initially this would be the same as weight. Then whenever weight is updated, it won't be overwriting the initial weight.

[Todd88]

Thanks a lot. It was simpler than I thought Thanks!