Grade book program using arrays and Bubble sort (many problems)

[xtheendx]

I am writing a gradbook type program. It first allows the user to enter the number of students they want to enter. then allows them to enter the first name, last name, and grade of each student. The program then should sort the names alphabetically by last name and display a list of all the students names and grades in alphabetical order. I have completed all my functions and classes, but i am getting a god aweful amount of errors and i am not sure what is wrong. It is my first attempt at using classes and objects and bubble sort so i am not sure. here is my code let me know any problems you see, i would greatly appreciate some guidance. First is the header file

#include <iostream>  // allows the program to output data to the screen
 
// students class definition
class students
{
public:
    int arraySize; // size of array entered by user for number of students
 
    int getNumstudents(int arraySize); // function to get the number of students user wants to enter
    void getData(int arraySize); // function to get first and last name and the students grade
    void displayMessage(); // displays welcome message
    void sortData (); // function to alphabetize by last name using buble sort
    void printData (); // function to print data
private:
    char*firstName[arraySize]; // array of students first names
    char*lastName[arraySize]; // array of students last names
    int grades[arraySize]; // array of students grades
};
 

and here is the cpp file

 #include <iostream>  // allows the program to output data to the screen
#include <conio.h>
#include  <iomanip>
#include <cstdlib>
#include <string.h>
#include "students.h" // gradebook class defintion
 
 
using std::cout; // program uses cout
using std::cin; // program uses cin
using std::endl; // program uses endl
using std::setprecision; // set numeric output precision
using std::fixed; // ensures that decimal point is displayed
using std::setw;
 
 
void  students::displayMessage()
{
 
    cout << "Welcome to the Student Scores Application." << endl;
}
 
// sorts data alphabetically by last name using bubble sort    
void students::sortData()
{
 
    for(int i = 0; i < arraySize ; i++){
            for(int j = i+1; i < arraySize; j++){
                  if(strcmp(lastName[i]){
                    char *temp = lastName[i];    // swap pointers
                    lastName[i] = lastName[j];
                    lastName[j] = temp;
                }
              }
        }
 }
 
// Prints all the students data
void students::printData()
{
 
    for (int i = 0; i < arraySize; i++)
    {
 
    cout << "Student " << num << " last name: " << lastName[i] <<", " << firstName[i] << ": " << grades[i] << endl;
 
    }
}
 
// gets the number of students the user wnats to enter and sets that as the arraysize
int students::getNumstudents(int arraySize)
{
    cout << "Enter number of students to enter: ";
    cin >> arraySize;
}
 
// gets students info from user
void students::getData(int arraysize)
{
    int num = 1;
    char*userinput1;
    char*userinput2;
    int userinput3;
 
    while ( num <= arraySize){
 
    cout << "Student " << num << " last name: ";
 
    lastName[arraysize] = userinput1;
 
    cout << "Student " << num << " first name: ";
 
    firstName[arraysize] = userinput2;
 
    cout << "Student " << num << " score: ";
 
    grades[arraysize] = userinput3;
 
    num++
    }
}
 
// function main begins program exectuion
int main() 
{
 
 
    students.displayMessage();
 
    students.getNumstudents();
 
    students.getData();    
 
    students.sortData();
 
    students.printData();
}
 

[oler1s]

Ok, I guess I made things a bit more confusing...

int  numItems = 1;
std::vector<int> numbers(numItems);
numbers[0] = 50;
for (int i =0; i<= numItems; ++i)
{
    std:: cout << numbers[i] << '\n';
}
 

Let's run through this.

Output:
i    i<=numItems    numbers[i]
0    0<=1 true      numbers[0]==50
1    1<=1 true      numbers[1]==?
 

Do you see the problem?


And don't worry about the whole declaring i thing. I guess I pulled out the wrong idea with it. It's a design issue you have in your class, and you'll realize it soon enough.

[xtheendx]

Ok, I guess I made things a bit more confusing...

int  numItems = 1;
std::vector<int> numbers(numItems);
numbers[0] = 50;
for (int i =0; i<= numItems; ++i)
{
    std:: cout << numbers[i] << '\n';
}
 

Let's run through this.

Output:
i    i<=numItems    numbers[i]
0    0<=1 true      numbers[0]==50
1    1<=1 true      numbers[1]==?
 

Do you see the problem?


And don't worry about the whole declaring i thing. I guess I pulled out the wrong idea with it. It's a design issue you have in your class, and you'll realize it soon enough.

I understand the problem in the example you gave. Becasue numbers[0] = 50 that when the for loop tries to call numbers[1] there is nothing there, even though the condition is true....wait are you saying that when i am setting myy for loop to i <= numStudents, that when it gets to that last element there is nothing there because the vector starts at 0 and numstudents starts at 1. so i would set the for loop to i <= numStudents -1. that makes since...but then again maybe i am completly wrong again. I apologize if i am complety wrong again, i dont mean to waste you time, but i really appreciate it. I have been up for the past 24 hrs working on this program , i think i just need to sleep and it will make more sense in the morning. ill give it a try though beforei hit the sack.. thanks again.

[Ganon11]

I understand the problem in the example you gave. Becasue numbers[0] = 50 that when the for loop tries to call numbers[1] there is nothing there, even though the condition is true....wait are you saying that when i am setting myy for loop to i <= numStudents, that when it gets to that last element there is nothing there because the vector starts at 0 and numstudents starts at 1. so i would set the for loop to i <= numStudents -1. that makes since...but then again maybe i am completly wrong again. I apologize if i am complety wrong again, i dont mean to waste you time, but i really appreciate it. I have been up for the past 24 hrs working on this program , i think i just need to sleep and it will make more sense in the morning. ill give it a try though beforei hit the sack.. thanks again.

i <= numStudents -1

Will work and accomplish your goal, or you could write

i < numStudents

which will do the same thing.

Basically, because arrays and vectors are 0 indexed (that is, the first element is at index 0), the last index is always size - 1. So, in a vector of size 5, the elements are at index 0, 1, 2, 3, and 4. There is no guarantee that anything useful can be found in index 5.

[xtheendx]

hey man thanks that worked wonders. I have edited the code and it does run smoother and doesnt crash. The problem i run into now is that when i run it last name and first name are displayed at the same time for the user to enter. Like this last name: first name:. How get them to be seperate so the user can enter them individually. Also it not sorting them but i think it has to do with the program not getting the first and last name seperatly.

 #include <iostream>  // allows the program to output data to the screen
#include <conio.h>
#include  <iomanip>
#include <cstdlib>
#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include "students.h" // gradebook class defintion
 
 
using std::cout; // program uses cout
using std::cin; // program uses cin
using std::endl; // program uses endl
using std::setprecision; // set numeric output precision
using std::fixed; // ensures that decimal point is displayed
using std::setw;
using std::string;
using std::vector;
 
 
void  students::displayMessage()
{
 
    cout << endl << "Welcome to the Student Scores Application." << endl << endl;
}
 
 
void students::getData()
{
    int numStudents = 0;
    string name;    
    int score = 0;
    int i = 0;
 
    cout <<"Enter number of students to enter: ";
    cin >> numStudents;
 
    vector<string> student_lastnames(numStudents);
    vector<string> student_firstnames(numStudents);
    vector <int> student_score(numStudents);
 
    do
 
    { 
            cout << "Student " << i + 1 <<" last name: "; 
            getline (cin, name);
              student_lastnames.push_back(name);
 
            cout << "Student " << i + 1 <<" first name: "; 
            getline (cin, name);
             student_firstnames.push_back(name);
 
            cout << "Student " << i + 1 <<" score: "; 
            cin >> score;
        student_score.push_back(score);
 
     i++;
     }
 
     while ( i < numStudents);
 
 
            // sort them alphabetically
        sort (student_lastnames.begin(), student_lastnames.end());
 
    for (int l =0; l < student_lastnames.size(); l++)
    {
            cout << student_lastnames[l] << " " << student_firstnames[l] << " " << student_score[l];
    }
 
 
 
}
 
// function main begins program exectuion
int main() 
{
    students mystudent;
 
    mystudent.displayMessage();
 
    mystudent.getData();    
 
} 

[xtheendx]

now the user can enter all the info indivudally. And it the sort works... the problem i run into now is that for some reason when it prints it always priints two zeros before the text. and while it sorts the last names it prints the last name that is sorted withe first name and score of the first entry. ex. user inputs
studnt 1 last name: oaks
student 1 first name: john
student 1 grade: 100

studnt 2 last name: hill
student 2 first name: mike
student 2 grade: 75

program prints out:

0 0 hill john 100 oaks mike 75

i realize that since i am just sorting the lastname vector, that it is storing the sorted last name with the user input of the first name. not sure how to fix it and get rid of the zeros. thanks for the help so far.

 #include <iostream>  // allows the program to output data to the screen
#include <conio.h>
#include  <iomanip>
#include <cstdlib>
#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <fstream>
#include <ios>
#include <istream>
#include <limits>
#include "students.h" // gradebook class defintion
 
 
using std::cout; // program uses cout
using std::cin; // program uses cin
using std::endl; // program uses endl
using std::setprecision; // set numeric output precision
using std::fixed; // ensures that decimal point is displayed
using std::setw;
using std::string;
using std::vector;
using std::max;
 
 
void  students::displayMessage()
{
 
    cout << endl << "Welcome to the Student Scores Application." << endl << endl;
}
 
 
void students::getData()
{
    int numStudents = 0;
    string name;    
    int score = 0;
    int i = 0;
 
    cout <<"Enter number of students to enter: ";
    cin >> numStudents;
    cin.ignore ( std::numeric_limits<std::streamsize>::max(), '\n' );
 
    vector<string> student_lastnames(numStudents);
    vector<string> student_firstnames(numStudents);
    vector <int> student_score(numStudents);
 
    do
 
    { 
            cout << "Student " << i + 1 <<" last name: "; 
            cin >> name;
              cin.ignore ( std::numeric_limits<std::streamsize>::max(), '\n' );    
        student_lastnames.push_back(name);
 
 
 
 
            cout << "Student " << i + 1 <<" first name: "; 
            cin >> name;
             cin.ignore ( std::numeric_limits<std::streamsize>::max(), '\n' );
        student_firstnames.push_back(name);
 
            cout << "Student " << i + 1 <<" score: "; 
            cin >> score;
        cin.ignore ( std::numeric_limits<std::streamsize>::max(), '\n' );    
        student_score.push_back(score);
 
     i++;
     }
 
     while ( i < numStudents);
 
 
            // sort them alphabetically
        sort (student_lastnames.begin(), student_lastnames.end());
 
    for (int l =0; l < student_lastnames.size(); l++)
    {
            cout << student_lastnames[l] << " " << student_firstnames[l] << " " << student_score[l];
    }
 
 
 
}
 
// function main begins program exectuion
int main() 
{
    students mystudent;
 
    mystudent.displayMessage();
 
    mystudent.getData();    
 
}