从文件中读取字符串并进行排序

Question

I need help with my assignment. I am not allowed to use any functions other than loops, if statements, cout, cin, basic operators and basic string. Arrays are not allowed. I need to sort a list of names from a file by alphabetical order and output which names would be at the front and back of the line. However when I try to run my code it stops at the part where it reads the file. The file is in the correct location because I hae tested it with cout. I cant figure out what I am doing wrong. Any help would be appreciated! Heres the code:

#include<iostream>
#include<string>
#include<fstream>
using namespace std;

int main()
{

    //Intialize variables
    string studentName;
    string firstEntry;
    string secondEntry;
    string first;
    string last;
    ifstream inputFile;
    string filename;
    int students;

    //Ask for amount of students
    cout << "Please enter the number of students in the class.\n(The number must be a whole number between 1 and 25.)\n";
    cin >> students;

    //Input validation
    while (students < 1 || students > 25)
    {
        cout << "\nInvalid value. Please enter a value between 1 and 25.\n";
        cin >> students;
    }

    //Get file name from user
    cout << "Please enter the name of the file with the list of students\n";
    cin >> filename;

    //Open the file
    inputFile.open(filename);
    if (inputFile)
    {
        while (inputFile >> studentName)
        {
            cin >> studentName;
            studentName = firstEntry;
            cin >> studentName;
            studentName = secondEntry;
            do
            {
                if (firstEntry < secondEntry)
                {
                    firstEntry = first;
                    secondEntry = last;
                }
                else
                {
                    firstEntry = last;
                    secondEntry = first;
                }
            } while (students = 30);

            if (firstEntry < first)
                firstEntry = first;

            if (secondEntry < first)
                secondEntry = first;

            if (firstEntry > last)
                firstEntry = last;

            if (secondEntry > last)
                secondEntry = last;

        }
        cout << first << " is the first student in line.";
        cout << last << " is the last student in line.";
    }
    else
    {
        cout << "Error opening the file.\nPlease restart the program and try again.";
        return 1;
    }

    inputFile.close();
    return 0;
}

Answer 1

         cin >> studentName;

This is why your program stops. It is waiting for you to type something at the keyboard. (cin is the standard input in C++)

Answer 2

My sincere advise would be always use pen and paper and note down your requirement first. Base on that write down the algorithm and convert that algorithm into code. What are you doing in your codes are all wrong unfortunately. Just deeply think what are you doing in your code specially below codes:-

   while (inputFile >> studentName)//Think what are you doing here?
    {
        cin >> studentName;//???? reading into the same variable
        studentName = firstEntry;//???? what are your doing here no value in firstEntry
        cin >> studentName;//??here
        studentName = secondEntry;//?? here no value in secondEntry
        do
        {
            if (firstEntry < secondEntry)// this is not correct string comparison  
            {
                firstEntry = first;//?? no value in first
                secondEntry = last;//?? no value in last
            }

If you consider all this very carefully you will understand all your mistakes.

Hope this will help you..