Question

Update your first program to dynamically allocate the item ID and GPA arrays. The number of items will be the first number in the updated “student2.txt” data file. A sample file is shown below:

3

1827356 3.75

9271837 2.93

3829174 3.14

Your program should read the first number in the file, then dynamically allocate the arrays, then read the data from the file and process it as before. You’ll need to define the array pointers in main and pass them into your “read data” function by reference so that the addresses stored into them go back to main and can be used by the rest of the program.

Demonstrate your pointer prowess by converting your array notation to pointer notation in the binSearch function for this revised program.

Pass by pointer reference, Read Size out of data files, do NEW to allocate arrays

1. Pass in pointers by reference
2. Either return the size or use a reference parameter (with &) for size
3. In function:

1. Create and connect the file stream, checking for error
2. Read the size (1^st number in the file)
3. Allocate the arrays, using new
4. Read the data as before

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

#include <iostream>
#include <iomanip>
#include <fstream>
#include <cstdlib>

using namespace std;

void readData(long int studentID[],double gpa[],int &size);
void selectionSort(long int studentID[],double gpa[],int size);
int binSearch(long int studentID[],double gpa[],int size,long int searchNumber);
long int readStudentID();
void printStats(long int studentID,double gpa);

int main()
{ long int* sptr;
int i=0,size;
long int studentID[25];
double* gptr;
double gpa[25] ;

//Read all 25 Student ID and corresponding GPA into parallel arrays from a text file
readData(studentID,gpa,size);

//Use a selection sort to sort the arrays by Student ID.
selectionSort(studentID,gpa,size);

//Read in a Student ID from user, loop back to allow user to continue
long int searchStudentID;

while(true)
{
searchStudentID = readStudentID();
//Terminate loop when -99 entered
if(searchStudentID=="-99")
break;
//Binary search to locate student id once they have been sorted.
int index=binSearch(studentID,gpa,size,searchStudentID);
if(index==-1){
cout<<"\nStudent ID Not Found!\n";
}
else{
printStats(studentID[index],gpa[index]);
}
}
cout<<"-----------------------\n";
cout<<"Thank you for searching\n";
return 0;
}

void readData(long int studentID[],double gpa[],int &size)
{
int i=0;
cout<<"Reading data from student.txt file\n";
ifstream infile;
infile.open("student.txt");
while (!infile.eof())
{
infile >> studentID[i] >> gpa[i];
i++;
}
size = i-1;

}

void selectionSort(long int studentID[],double gpa[],int size)
{
int i,j,min;
long int temp;
double tempgpa;
for(i=0;i<size-1;i++)
{
min=i;
for(j=i+1;j<size;j++)
{
if(studentID[j]<studentID[min])
{
min=j;
}
}
temp=studentID[i];
studentID[i]=studentID[min];
studentID[min]=temp;

tempgpa=gpa[i];
gpa[i]=gpa[min];
gpa[min]=tempgpa;
}
}

int binSearch(long int studentID[],double gpa[],int size,long int searchNumber)
{

int first, last, middle;
int location = -1;

first = 0;
last = size-1;
while (location == -1 && first <= last)
{
middle = (first + last) / 2;

if (searchNumber > studentID[middle])
first = middle + 1;
else if (searchNumber < studentID[middle])
last = middle - 1;
else
location = middle;
}
return location;
}

long int readStudentID()
{
long int searchStudentID;
cout<<"Enter Student ID to search (-99 to exit)\n";
cin>>searchStudentID;
return searchStudentID;
}

void printStats(long int studentID,double gpa)
{
cout<<"Student ID \tGPA\n";
cout<<"----------------------------\n";
cout<<studentID<<"\t\t"<<gpa<<"\n";
}

Answer 1

Updated code

#include <iostream>
#include <iomanip>
#include <fstream>
#include <cstdlib>

using namespace std;

void readData(long int studentID[],double gpa[],int &size);
void selectionSort(long int studentID[],double gpa[],int size);
int binSearch(long int studentID[],double gpa[],int size,long int searchNumber);
long int readStudentID();
void printStats(long int studentID,double gpa);

int main()
{
  
   int i=0,size;
   long int *studentID;
   ifstream inFile;
   double *gpa;
   inFile.open("student2.txt");
   if(!inFile)
   {
       cout<<"Error in opening the file.. Exiting!......"<<endl;
       return 0;
   }
   inFile>>size;
   studentID=new long[size];
   gpa=new double[size];
   inFile.close();
   //Read all 25 Student ID and corresponding GPA into parallel arrays from a text file
   readData(studentID,gpa,size);

   //Use a selection sort to sort the arrays by Student ID.
   selectionSort(studentID,gpa,size);

   //Read in a Student ID from user, loop back to allow user to continue
   long int searchStudentID;

   while(true)
   {
       searchStudentID = readStudentID();
       //Terminate loop when -99 entered
       if(searchStudentID==-99)
       break;
       //Binary search to locate student id once they have been sorted.
       int index=binSearch(studentID,gpa,size,searchStudentID);
       if(index==-1)
       {
           cout<<" Student ID Not Found! ";
       }
       else
       {
           printStats(studentID[index],gpa[index]);
       }
   }
   cout<<"----------------------- ";
   cout<<"Thank you for searching ";
   return 0;
}
void readData(long int studentID[],double gpa[],int &size)
{
   ifstream inFile;
   int i=0;
   inFile.open("student2.txt");
   if(!inFile)
   {
       cout<<"Error in opening the file.. Exiting!......"<<endl;
       return;
   }
   inFile>>size;
  
   while(!inFile.eof())
   {
       inFile>>studentID[i]>>gpa[i];
       i++;
   }
   inFile.close();
}
void selectionSort(long int studentID[],double gpa[],int size)
{
   int i,j,min;
   long int temp;
   double tempgpa;
   for(i=0;i<size-1;i++)
   {
       min=i;
      
       for(j=i+1;j<size;j++)
       {
           if(studentID[j]<studentID[min])
           {
               min=j;
           }
       }
       temp=studentID[i];
       studentID[i]=studentID[min];
       studentID[min]=temp;

       tempgpa=gpa[i];
       gpa[i]=gpa[min];
       gpa[min]=tempgpa;
   }
}
int binSearch(long int studentID[],double gpa[],int size,long int searchNumber)
{
   int first, last, middle;
   int location = -1;

   first = 0;
   last = size-1;
   while (location == -1 && first <= last)
   {
       middle = (first + last) / 2;
       if (searchNumber > studentID[middle])
           first = middle + 1;
       else if (searchNumber < studentID[middle])
           last = middle - 1;
       else
           location = middle;
   }
   return location;
}
long int readStudentID()
{
   long int searchStudentID;
   cout<<"Enter Student ID to search (-99 to exit) ";
   cin>>searchStudentID;
   return searchStudentID;
}
void printStats(long int studentID,double gpa)
{
   cout<<"Student ID GPA ";
   cout<<"---------------------------- ";
   cout<<studentID<<" "<<gpa<<" ";
}

ouptut

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