C++多維排序

Question

我寫了一個基本程序，收集學生的姓名和答案，並自動爲他們評分。最後，我想用相應的名字按降序排列分數。我瞭解如何對得分進行排序，但不能與學生姓名結合使用。這是我迄今爲止所擁有的。

#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; 
} 

現在，它按降序對得分進行排序，但與得分輸出的名稱不正確。

Answer 1

你需要以某種方式'連接'學生的名字與他/她的分數。一個非常簡單和直接的方法是創建一個結構，即

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

接下來，您需要定義一個比較函數（看看這裏的一個例子：http://www.cplusplus.com/reference/algorithm/sort/），這樣就可以使用std:sort排序的Student個矢量。你比較功能可以喜歡這樣：

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

Answer 2

爲了保持自己在做什麼的精神，你可以對一個向量，這裏是一個代碼示例：

#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; 
}