Array not initializing properly within a while loop - c++

My issue is that I have set up an array to store totals that were calculated from values read from a file. These stored totals are then added together to find the over all average.
This issue is stemming from a 'cin' at the beginning of the program where the user inputs a number and that number is supposed to drive the program by setting how many times the program loops and how many modules are inside the array. The array does not seem to work properly no matter how much I try.
#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
using namespace std;
int main()
{
string StudentGrades;
int studentID;
double quiz1;
double quiz2;
double quiz3;
double quiz4;
int total = 0;
double choice;
ofstream outFile;
double numStud=1;
cout << "Enter student ID number, Quiz 1 Grade, Quiz 2 Grade , Quiz 3 Grade, Quiz 4 Grade" << endl;
outFile.open("StudentGrades.txt");
cout << "How many students would you like to enter?" << endl;
cin >> numStud;
for (int x = 0; x < numStud; x++)
{
cout << "Enter student ID: ";
cin >> studentID;
cout << "Enter quiz grade 1: ";
cin >> quiz1;
//cout << quiz1;
cout << "Enter quiz grade 2: ";
cin >> quiz2;
//cout << quiz2;
cout << "Enter quiz grade 3: ";
cin >> quiz3;
//cout << quiz3;
cout << "Enter quiz grade 4: ";
cin >> quiz4;
//cout << quiz4;
cout << endl;
//outFile.open("StudentGrades.txt");
if (outFile.is_open())
{
cout << "inside if/else outFile" << endl;
//outFile << "File successfully open";
outFile << studentID << " " << quiz1 << " " << quiz2 << " " << quiz3 << " " << quiz4 << endl;
}
else
{
cout << "Error opening file";
}
outFile.close();
/*cout << "Enter 0 for no more students. Enter 1 for more students." << endl;
cin >> choice;
if (choice == 1)
continue;
if (choice == 0)
{
outFile.close();
break;
}*/
}
ifstream inFile;
inFile.open("StudentGrades.txt");
int sTotal;
int total[numStud];
while (inFile >> studentID >> quiz1 >> quiz2 >> quiz3 >> quiz4)
{
//cout << studentID << " " << quiz1 << " " << quiz2 << " " << quiz3 << " " << quiz4 << endl;
total = (quiz1 + quiz2 + quiz3 + quiz4);
sTotal = total[numStud];
double avg = total / 4;
}
system("pause");
return 0;
}

int total[numStud]; is a variable length array and is not standard in C++. If you need an array and you don't know what the size will be then you should use a std::vector. A vector can be used almost exactly as an array can. For example you could would become:
int total;
std::vector<int> studentTotal;
while (inFile >> studentID >> quiz1 >> quiz2 >> quiz3 >> quiz4)
{
//cout << studentID << " " << quiz1 << " " << quiz2 << " " << quiz3 << " " << quiz4 << endl;
studentTotal.push_back(quiz1 + quiz2 + quiz3 + quiz4); // insert into the vector at the end
total += studentTotal.back(); // get last inserted element
}

Related

Salary with vector array to get sum of employee gross pay

I am to create an application that takes at least 5 employees i.d, names, pay rate, and hours. And then I am to add the pay rate and the hours together to show the gross pay for each employee at the end of the initial inquiries. I am stuck on how to add it in the vector please help!
** Here is the assignment that our instructor gave us **
http://itweb.fvtc.edu/ag/?u=3&f=cpp-assignment4
I've added a vector and added all the essential information for the employee
#include <iostream>
#include <conio.h>
#include <string>
#include <vector>
using namespace std;
struct Employee
{
int id;
string firstName;
string lastName;
float payRate;
int hours;
};
int main()
{
/*========= other way of adding employee information ==========*/
/*const int NUM_EMPLOYEE = 5;
Employee employee[NUM_EMPLOYEE];
for (int i = 0; i < 5; i++)
{
cout << "ID of employee " << (i + 1) << ": ";
cin >> employee[i].id;
cout << "First Name of employee " << (i + 1) << ": ";
cin >> employee[i].firstName;
cout << "Last Name of employee " << (i + 1) << ": ";
cin >> employee[i].lastName;
cout << "Pay rate for employee " << (i + 1) << ": ";
cin >> employee[i].payRate;
cout << "Hours worked " << (i + 1) << ": ";
cin >> employee[i].hours;
}*/
/*========= End of other way of adding employee information ==========*/
vector<Employee> employees;
char Another = 'y';
while (Another == 'y' || Another == 'Y')
{
Employee e;
cout << "Enter employee ID: \n";
cin >> e.id;
cout << "Enter employee first name: \n";
cin >> e.firstName;
cout << "Enter employee last name: \n";
cin >> e.lastName;
cout << "Enter employee pay rate: \n";
cin >> e.payRate;
cout << "Enter employee hours worked: \n";
cin >> e.hours;
employees.push_back(e);
cout << "Another? (y/n): \n";
cin >> Another;
}
float sum = 0;
vector<Employee>::iterator it = employees.begin();
for (; it != employees.end(); it++)
{
cout << "ID of employee: \n" << it->id << ": \n"
<< "Employees name: \n" << it->firstName << " " << it->lastName << ": \n"
<< "Employee pay rate: \n" << it->payRate << ": \n"
<< "Employee hours worked: \n" << it->hours << "\n";
}
float avg = sum / employees.size();
Employee e;
/*cout << " ID of employees: \n" << e.id;
cout << " Name of employees: \n" << e.firstName << " " <<
e.lastName;*/
cout << "Gross pay of employees: \n" << avg;
_getch();
return 0;
}
Show Id, names, and gross pay of all employees to user
vector<Employee> employees;
char Another = 'y';
while (Another == 'y' || Another == 'Y')
{
Employee e;
cout << "Enter employee ID: \n";
cin >> e.id;
cout << "Enter employee first name: \n";
cin >> e.firstName;
cout << "Enter employee last name: \n";
cin >> e.lastName;
cout << "Enter employee pay rate: \n";
cin >> e.payRate;
cout << "Enter employee hours worked: \n";
cin >> e.hours;
employees.push_back(e);
cout << "Another? (y/n): \n";
cin >> Another;
}
float sum = 0;
vector<Employee>::iterator it = employees.begin();
cout << "ID" << "\t" << "First Name" << "\t" << "Last Name" << "\t" << "Pay rate" << "\t" << "Hours" << "\t" << "Gross Pay" << "\n" ;
for (; it != employees.end(); it++)
{
float grossPay = it->payRate * it->hours;
cout << it->id << "\t" << it->firstName << "\t\t" << it->lastName << "\t\t" << it->payRate << "\t\t"
<< it->hours << "$" << "\t" << grossPay << "\n";
sum += grossPay;
}
cout << "The gross pay for all employee is: " << "$" << sum;
_getch();
return 0;
}
//This is what i got so far. But if I want to make the application ask the user to input how many employee they want to enter into the database how do i do that? would it be like this?
int EMPLOYEE_NUM[][] // ??

I don't know how to write the average grade with variables

I'm trying to automatically set the number of the given variables, for example:
char subject1[30];
char subject2[30];
char subject3[30];
float grade1;
float grade2;
float grade3;
cout << "Type in your first subject: " ;
cin >> subject1;
cout << "Type in your second subject: ";
cin >> subject2;
cout << "Type in your third subject: ";
cin >> subject3;
cout << "Type in your grade for: " << subject1 << " :";
cin >> grade1;
cout << "Type in your grade for: " << subject2 << " :";
cin >> grade2;
cout << "Type in your grade for: " << subject3 << " :";
cin >> grade3;
float sum = grade1 + grade2 + grade3;
float average = (sum / 3);
cout << "AVERAGE GRADE";
cout << "************************************" << endl;
cout << subject1 << grade1 << endl;
cout << subject2 << grade2 << endl;
cout << subject3 << grade3 << endl;
cout << "====================================" << endl;
cout << "Average: " << average << endl;
return 0;
The code that calculates it works but I was wondering as how do I put the 3 grades that user inputed. So I don't have to go edit the calculation part every time I add another subject. I'm not sure if I explained well as to what I meant but I hope you understand.
A simple solution would be to store everything in a vector (that's preferred most of the time over the char array you used) an then just loop for the amount of subjects you have.
#include <vector> // need to inlcude this to be able to use vector
#include <iostream>
const int numSubjects = 3;
std::vector<std::string> prefix{"first", "second", "third"};
std::vector<std::string> subjects(numSubjects);
std::vector<float> grades(numSubjects);
for(int i = 0; i < numSubjects; i++) {
std::cout << "Type in your " << prefix[i] << " subject: ";
std::cin >> subjects[i];
std::cout << "Type in your grade for " << subjects[i] << ": ";
std::cin >> grades[i];
}
//afterwards do the calculations
Note that I initialized the vectors with a size of numSubjects that way you can access and write to indices of the vector with the [] operator. If you don't initialize vector with a size then you can use push_back() to insert elements.

Break statement is not in loop or switch statement?

I am having trouble with my code, I have read other forums this site about this problem but they don't really relate to my situation. I am new to C++, I barely have about 3 weeks into the course. I do not know why my break statement isn't working, to me it is in the loop. What am I missing?
float a[60][7];
int row;
cout << "How many students would you like to grade?" << endl;
cin >> studentNum;
cout << "Enter grades for the first student" << endl;
row = 0;
n = studentNum - 2;
while (row < studentNum)
{
a[row][0]=k;
a[row][0] = row;
cout << "Enter grade for test 1: ";
cin >> a[row][1];
cout << "Enter grade for test 2: ";
cin >> a[row][2];
cout << "Enter grade for test 3: ";
cin >> a[row][3];
cout << "Enter grade for test 4: ";
cin >> a[row][4];
a[row][5] = (a[row][1] + a[row][2] + a[row][3] + a[row][4]) / 4;
a[row][6] = a[row][1] * 0.2 + a[row][2] * 0.3 + a[row][3] * 0.3 + a[row][4] * 0.2;
row++;
}
if (row == n)
{
cout << "Enter Grades for the last Student" << endl;
cout << "Enter grade for test 1: ";
cin >> a[row][1];
cout << "Enter grade for test 2: ";
cin >> a[row][2];
cout << "Enter grade for test 3: ";
cin >> a[row][3];
cout << "Enter grade for test 4: ";
cin >> a[row][4];
break;
}
else
{
cout << "Enter grades for the next student" << endl;
row = row + 1;
}
cout << "Stdnt" << "\t" << "Grade1" << "\t" << "Grade2" << "\t" << "Grade3" << "\t" << "Grade4" << "\t" << "Avg1" << "\t" << "Avg2" << endl;
printarray(a, studentNum);
cin.get();
return 0;
Something like this?
float a[60][7];
int row = 0;
std::cout << "How many students would you like to grade?" << std::endl;
std::cin >> studentNum;
n = studentNum - 2;
std::cout << "Enter grades for the first student" << std::endl;
while (row <= n)
{
a[row][0] = k;
a[row][0] = row;
std::cout << "Enter grade for test 1: ";
std::cin >> a[row][1];
std::cout << "Enter grade for test 2: ";
std::cin >> a[row][2];
std::cout << "Enter grade for test 3: ";
std::cin >> a[row][3];
std::cout << "Enter grade for test 4: ";
std::cin >> a[row][4];
a[row][5] = (a[row][1] + a[row][2] + a[row][3] + a[row][4]) / 4;
a[row][6] = a[row][1] * 0.2 + a[row][2] * 0.3 + a[row][3] * 0.3 + a[row][4] * 0.2;
if (row==n)
{
std::cout << "Enter Grades for the last Student" << std::endl;
std::cout << "Enter grade for test 1: ";
std::cin >> a[row][1];
std::cout << "Enter grade for test 2: ";
std::cin >> a[row][2];
std::cout << "Enter grade for test 3: ";
std::cin >> a[row][3];
std::cout << "Enter grade for test 4: ";
std::cin >> a[row][4];
}
else
{
std::cout << "Enter grades for the next student" << std::endl;
}
row++;
}
std::cout << "Student" << "\t" << "Grade1" << "\t" << "Grade2" << "\t" << "Grade3" << "\t" << "Grade4" << "\t" << "Avg1" << "\t" << "Avg2" << std::endl;
printarray(a, studentNum);
std::cin.get();
return 0;
P.S. edit with fixed while

How to call multiple numbers from a file [closed]

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I was wondering if someone could help me with my code. I am not sure how to call specific values from a text file that had values put into it by the user.
the text file would look like this
1000 90 80 50 60
1001 60 70 100 90
1002 100 30 50 70
I need to add each of the numbers after the 4-digit number and then divide them.
I want to be able to do this through a nested loop.
#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
using namespace std;
int main()
{
string StudentGrades;
int studentID;
double quiz1;
double quiz3;
double quiz4;
double total = 0;
double choice;
ofstream outFile;
cout << "Enter student ID number, Quiz 1 Grade, Quiz 2 Grade , Quiz 3 Grade, Quiz 4 Grade" << endl;
outFile.open("StudentGrades.txt");
//while (outFile.open)
//{
for (int x = 0; x < 4; x++)
{
cout << "Enter student ID: ";
cin >> studentID;
cout << "Enter quiz grade 1: ";
cin >> quiz1;
//cout << quiz1;
cout << "Enter quiz grade 2: ";
cin >> quiz2;
//cout << quiz2;
cout << "Enter quiz grade 3: ";
cin >> quiz3;
//cout << quiz3;
cout << "Enter quiz grade 4: ";
cin >> quiz4;
//cout << quiz4;
cout << endl;
//outFile.open("StudentGrades.txt");
if (outFile.is_open())
{
cout << "inside if/else outFile" << endl;
//outFile << "File successfully open";
outFile << studentID << " " << quiz1 << " " << quiz2 << " " << quiz3 << " " << quiz4 << endl;
}
else
{
cout << "Error opening file";
}
cout << "Enter 0 for no more students. Enter 1 for more students." << endl;
cin >> choice;
if (choice == 1)
continue;
if (choice == 0)
{
outFile.close();
break;
}
}
//}
//declaring file and opening it
ifstream inFile;
inFile.open("StudentGrades.txt");
while (inFile >> studentID<<)
{
cout << studentID << quiz1 << quiz2 << quiz3 << quiz4 << endl;
}
system("pause");
return (0);
}
This would be the idiomatic loop for reading a file of that format:
while (inFile >> studentID >> quiz1 >> quiz2 >> quiz3 >> quiz4)
{
// Do some arithmetic
}
I have no idea what good a nested loop would do.
this should work
#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
using namespace std;
int main()
{
string StudentGrades;
int studentID;
double quiz1;
double quiz2;
double quiz3;
double quiz4;
double total = 0;
double choice;
ofstream outFile;
cout << "Enter student ID number, Quiz 1 Grade, Quiz 2 Grade , Quiz 3 Grade, Quiz 4 Grade" << endl;
outFile.open("StudentGrades.txt");
for (int x = 0; x < 4; x++)
{
cout << "Enter student ID: ";
cin >> studentID;
cout << "Enter quiz grade 1: ";
cin >> quiz1;
//cout << quiz1;
cout << "Enter quiz grade 2: ";
cin >> quiz2;
//cout << quiz2;
cout << "Enter quiz grade 3: ";
cin >> quiz3;
//cout << quiz3;
cout << "Enter quiz grade 4: ";
cin >> quiz4;
//cout << quiz4;
cout << endl;
//outFile.open("StudentGrades.txt");
if (outFile.is_open())
{
cout << "inside if/else outFile" << endl;
//outFile << "File successfully open";
outFile << studentID << " " << quiz1 << " " << quiz2 << " " << quiz3 << " " << quiz4 << endl;
}
else
{
cout << "Error opening file";
}
cout << "Enter 0 for no more students. Enter 1 for more students." << endl;
cin >> choice;
if (choice == 1)
continue;
if (choice == 0)
{
outFile.close();
break;
}
}
ifstream inFile;
inFile.open("StudentGrades.txt");
while (inFile >> studentID >> quiz1 >> quiz2 >> quiz3 >> quiz4)
{
cout << studentID << " " << quiz1 << " " << quiz2 << " " << quiz3 << " " << quiz4 << endl;
}
return 0;
}
you need to read the scores in that file and store in every designated variable
while (inFile >> studentID >> quiz1 >> quiz2 >> quiz3 >> quiz4)
{
cout << studentID << " " << quiz1 << " " << quiz2 << " " << quiz3 << " " << quiz4 << endl;
}

How to read in specific numbers from a txt file C++

The problem I am having is that I do not know how to read a specific number out of a text file that was created and had values entered into it earlier in the program.
I was hoping to use a nested loop statement for reading in the values after the values of the quizes are read in I need to add up the values and average them out and this needs to happen multiple times
#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
using namespace std;
int main()
{
string StudentGrades;
int studentID;
double quiz1;
double quiz2;
double quiz3;
double quiz4;
double total=0;
double choice;
ofstream outFile;
cout << "Enter student ID number, Quiz 1 Grade, Quiz 2 Grade , Quiz 3 Grade, Quiz 4 Grade" << endl;
outFile.open("StudentGrades.txt");
//while (outFile.open)
//{
for (int x = 0; x < 4; x++)
{
cout << "Enter student ID: ";
cin >> studentID;
cout << "Enter quiz grade 1: ";
cin >> quiz1;
//cout << quiz1;
cout << "Enter quiz grade 2: ";
cin >> quiz2;
//cout << quiz2;
cout << "Enter quiz grade 3: ";
cin >> quiz3;
//cout << quiz3;
cout << "Enter quiz grade 4: ";
cin >> quiz4;
//cout << quiz4;
cout << endl;
//outFile.open("StudentGrades.txt");
if (outFile.is_open())
{
cout << "inside if/else outFile" << endl;
//outFile << "File successfully open";
outFile << studentID << " " << quiz1 << " " << quiz2 << " " << quiz3 << " " << quiz4 << endl;
}
else
{
cout << "Error opening file";
}
cout << "Enter 0 for no more students. Enter 1 for more students." << endl;
cin >> choice;
if (choice == 1)
continue;
if (choice == 0)
{
outFile.close();
break;
}
}
//}
//declaring file and opening it
ifstream inFile;
inFile.open("StudentGrades.txt");
while (inFile>>studentID)
{
cout << studentID<< quiz1 <<quiz2<<quiz3<<quiz4<< endl;
}
system("pause");
return (0);
}
You are not reading all the fields from the input file, you are reading just the studentID.
while (inFile>>studentID)
{
cout << studentID<< quiz1 <<quiz2<<quiz3<<quiz4<< endl;
}
Try:
while (inFile >> studentID >> quiz1 >> quiz2 >> quiz3 >> quiz4)
{
cout << studentID << quiz1 << quiz2 << quiz3 << quiz4 << endl;
}
Update
Below is my suggestion for a refactored program. It's good to create functions that perform specific tasks and then call them from a higher level function instead of jamming them all in one large function.
#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
using namespace std;
void saveStudentData(string const& filename)
{
int studentID;
double quiz1;
double quiz2;
double quiz3;
double quiz4;
// Use int type for choice, not double
int choice;
ofstream outFile(filename);
if (!outFile.is_open())
{
// Problem opening file.
cout << "Error opening file";
return;
}
cout << "Enter student ID number, Quiz 1 Grade, Quiz 2 Grade , Quiz 3 Grade, Quiz 4 Grade" << endl;
for (int x = 0; x < 4; x++)
{
cout << "Enter student ID: ";
cin >> studentID;
cout << "Enter quiz grade 1: ";
cin >> quiz1;
cout << "Enter quiz grade 2: ";
cin >> quiz2;
cout << "Enter quiz grade 3: ";
cin >> quiz3;
cout << "Enter quiz grade 4: ";
cin >> quiz4;
cout << endl;
outFile << studentID << " " << quiz1 << " " << quiz2 << " " << quiz3 << " " << quiz4 << endl;
cout << "Enter 0 for no more students. Enter 1 for more students." << endl;
cin >> choice;
if (choice == 0)
{
break;
}
}
}
void readStudentData(string const& filename)
{
int studentID;
double quiz1;
double quiz2;
double quiz3;
double quiz4;
double total=0;
ifstream inFile(filename);
while (inFile >> studentID >> quiz1 >> quiz2 >> quiz3 >> quiz4)
{
total = (quiz1 + quiz2 + quiz3 + quiz4);
cout << studentID << " " << quiz1 << " " << quiz2
<< " " << quiz3 << " " << quiz4 << " " << total << endl;
}
}
int main()
{
string filename("StudentGrades.txt");
saveStudentData(filename);
readStudentData(filename);
return (0);
}