[C++] What's wrong with my quiz answer

[Nyap]

so I'm doing a test on chapter 6 of my c++ tutorial and one of the questions is this:

Write the following program: Create a struct that holds a student’s name and grade (on a scale of 0-100). Ask the user how many students they want to enter. Dynamically allocate an array to hold all of the students. Then prompt the user for each name and grade. Once the user has entered all the names and grades, sort the list by grade (highest first). Then print all the names and grades in sorted order.

What's wrong with my answer (I know I should have used std::vector but I rushed the lesson on it because I just want to get out of this hellish chapter as soon as possible )?
http://pastebin.com/amSCY7ja

output:

How many students do you wish to enter?: 2
Shrek
50
Hitler
75

50 got a grade of 0
75 got a grade of 0

 

[Hikari06]

Well I don't know c++ very well but I would write something like this instead to begin:

1. for (int k; k<numberOfStudents; k++)
2. {
3. cin >> students[k].name;
4. cin >> students[k].grade;
5. }

 

[btoast777]

Well, right off the bat I see that in your main's for loop:

1. for (int student{}; student<numberOfStudents; ++student)
2. {
3. cin >> students[student].name;
4. cin >> students[student].name;
5. }

You set the student's name twice. That's why your students' names are always their grade number. Line 4 here should be "cin >> students[student].grade."

 

[Nyap]

Well I don't know c++ very well but I would write something like this instead to begin:

1. for (int k; k<numberOfStudents; k++)
2. {
3. cin >> students[k].name;
4. cin >> students[k].grade;
5. }

yeah i just noticed that
but the sorting algorithm doesn't work

 

[Wellington2k]

Why do you use "int start{}" and "++start" in your for loop? I've taken two college level programming classes in C++ and we never used this.
For a for loop, I do this:
for (int i=0; i<count; i++) {
//stuff here
}

EDIT: Also, where is your swap function?
EDIT2: Okay, so swap is actually a built-in function. Learn something new everyday.

 

[btoast777]

Two things I have noticed in your sort method:

First, on line 21, is that supposed to be a ">" sign? I'm a bit unfamiliar with the "start{}" expression, but I assume it sets "start" to 0. If that's the case then your loop will never run, since 0 will never be greater than the number of students you have!

Also, you might have a problem when you up your list count to 3 or higher. On line 23 you declare the highestscore and higheststudent. Because this code comes after your first for loop, the next time it goes through the loop it's gonna set those back to zero. (This is known as an issue with "scope," a term you may or may not have not seen in your reading so far). You should instead move line 23 to before that first for loop.

EDIT: Edited to add a little more info.

 

[Nyap]

Why do you use "int start{}" and "++start" in your for loop? I've taken two college level programming classes in C++ and we never used this.
For a for loop, I do this:
for (int i=0; i<count; i++) {
//stuff here
}

EDIT: Also, where is your swap function?
EDIT2: Okay, so swap is actually a built-in function. Learn something new everyday.

{} is uniform initialization which was introduced in C++11
my tutorial strongly reccomends using it because it help tell the difference between initialization and assignment, and a couple of other reasons aswell
and I'm too lazy to explain the difference between using ++ as a prefix and as a postfix

--------------------- MERGED ---------------------------

well I've made progress

void sortStudents(student *studentsToSort, int numberOfStudents)
{
  for (int start{}; start<(numberOfStudents-1); ++start)
  {
  int highestScore{studentsToSort[start].grade}, highestStudent{start};
  for (int current{start+1}; current<numberOfStudents; ++current)
  {
  if ((studentsToSort[current].grade)>highestScore)
  {
  highestScore=studentsToSort[current].grade;
  highestStudent=current;
  }
  }
  swap(studentsToSort[start].grade, highestScore);
  swap(studentsToSort[start].name, studentsToSort[highestStudent].name);
  }
}

How many students do you wish to enter?: 3
Shrek
75
Bloop
23
Hitler
45

Shrek got a grade of 75
Hitler got a grade of 45
Bloop got a grade of 45

 

[Wellington2k]

{} is uniform initialization which was introduced in C++11
my tutorial strongly reccomends using it because it help tell the difference between initialization and assignment, and a couple of other reasons aswell
and I'm too lazy to explain the difference between using ++ as a prefix and as a postfix

Okay, interesting. I'm pretty sure we were purposefully not taught much C++ 11 to allow our code to work anywhere.
Oh, and I know the difference between prefix and postfix, but I've never had to use prefix in a for loop.

 

[Nyap]

Oh, and I know the difference between prefix and postfix, but I've never had to use prefix in a for loop.

I'm pretty sure it wouldn't make much of a difference used in a for loop like that

--------------------- MERGED ---------------------------

Two things I have noticed in your sort method:

First, on line 21, is that supposed to be a ">" sign? I'm a bit unfamiliar with the "start{}" expression, but I assume it sets "start" to 0. If that's the case then your loop will never run, since 0 will never be greater than the number of students you have!

Also, you might have a problem when you up your list count to 3 or higher. On line 23 you declare the highestscore and higheststudent. Because this code comes after your first for loop, the next time it goes through the loop it's gonna set those back to zero. (This is known as an issue with "scope," a term you may or may not have not seen in your reading so far). You should instead move line 23 to before that first for loop.

EDIT: Edited to add a little more info.

Yeah, I used the wrong relational operator and I'm fully aware of scope

--------------------- MERGED ---------------------------

I've fixed it!

void sortStudents(student *studentsToSort, int numberOfStudents)
{
  for (int start{}; start<(numberOfStudents-1); ++start)
  {
  int highestScore{start}, highestStudent{start};
  for (int current{start+1}; current<numberOfStudents; ++current)
  {
  if ((studentsToSort[current].grade)>highestScore)
  {
  highestScore=current;
  highestStudent=current;
  }
  }
  swap(studentsToSort[start].grade, studentsToSort[highestScore].grade);
  swap(studentsToSort[start].name, studentsToSort[highestStudent].name);
  }
}

thnx for helping