c++ multidimensional sorting

Question

I have written a basic program that collects student names and answers and automatically scores them. At the end I'd like to sort the scores in descending order with the corresponding names. I understand how to sort the scores but not in combination with the student names. This is what I have so far.

#include "stdafx.h"
#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
using namespace std;


int _tmain(int argc, _TCHAR* argv[])
{
    //declare variables
    char choice;
    string studentName;
    vector<char> answers;
    vector<string> names;
    int getStudents();
    int getQuestions();

    //calls function to get number of questions
    int questions = getQuestions();

    //Get answers
    for (int i = 0; i < questions; ++i) {
        cout << "What is the answer for question " << i + 1 << endl;
        cin >> choice;
        answers.push_back(choice);
    }

    //Get number of students
    int students = getStudents();

    //Get student names
    for (int i = 0; i < students; i++) {
        cout << "Student " << i + 1 << ", what is your name?" << endl;
        cin >> studentName;
        names.push_back(studentName);
    }

    int score = 0;
    char studentAnswer;
    vector<char> userAnswer;
    vector<float> finalScore;

    //gets student answers
    for (int i = 0; i < students; i++) {
        score = 0;
        for (int j = 0; j < questions; j++) {
            cout << names[i] << ", what is your answer for question " << j + 1 << "?" << endl;
            cin >> studentAnswer;
            userAnswer.push_back(studentAnswer);
            if (userAnswer[i*questions+j] == answers[j])
                score = score + 1;
        }
        finalScore.push_back(score);
    }

    //outputs scores
    std::sort(finalScore.begin(), finalScore.end());
    for (int i = 0; i < students; i++) {
        cout << names[i] << " scored " << finalScore[i] << " out of " << questions <<
            " or " << (finalScore[i] / questions) * 100 << "%" << endl;
    }

    system("pause");
    return 0;
}

//function to get number of questions
int getQuestions()
{
    int questions;
    cout << "How many questions are there?" << endl;
    cin >> questions;
    return questions;
}

//function to get number of students
int getStudents()
{
    int students;
    cout << "How many students are there?" << endl;
    cin >> students;
    return students;
}

Right now, it sorts the scores in descending orders but the names that are output with the scores are incorrect.

Answer 1

To keep the spirit of what you are doing, you can make a vector of pairs, here is a code example:

#include<vector>
#include<string>
#include<iostream>
#include<algorithm>

int main()
{
  std::vector< std::pair<double,std::string> > my_student_list; //  first element is the grade, second is the name
  std::pair<double,std::string>  student1(2.,"name1"),student2(2.,"name2"),student3(1.,"name3");
  my_student_list.push_back(student1);
  my_student_list.push_back(student2);
  my_student_list.push_back(student3);

  std::sort(my_student_list.begin(),my_student_list.end()); // sort by grade

  // loop over the vector to print the sorted list
  for(std::vector< std::pair<double,std::string> >::iterator iterator = my_student_list.begin(); iterator != my_student_list.end(); iterator++){
    // iterator->second is the name, and iterator->first the associated grade
    std::cout << iterator->second << " " << iterator->first << std::endl;
  }
  return 0;
}

Answer 2

You need to somehow 'connect' student name with his/her score. A very easy and straightforward way is to create a struct, i.e.

typedef struct Student
{
    string student_name_;
    float student_score_;
} Student;

Next you need to define a Compare function (look here for an example: http://www.cplusplus.com/reference/algorithm/sort/) so that you can use std:sort to sort a vector of Students. Your Compare function could like like this:

bool myCompareFunction ( Student a, Student b) 
{ 
    return (a.student_score_ < b.student_score_);
}