C++学生类作业：实现自定义排序的学生数据管理程序

Got it, let's work through this C++ programming problem together. Here's a complete solution that meets all your requirements:

1. Define a Student Data Structure #

First, we'll create a struct to group each student's details—this makes it easy to handle and organize the related data:

#include <iostream>
#include <string>

using namespace std; // For simplicity in a small program; you can avoid this in larger projects by qualifying with std::

struct Student {
    string lastName;
    string firstName;
    double gpa;
};

2. Read Input from Standard Input #

We'll read student entries until we hit the end of input (EOF) or reach the maximum limit of 50 students. Each entry follows the format: lastName firstName GPA:

int readStudents(Student students[], int maxSize) {
    int count = 0;
    // Keep reading until we hit max students or no more input
    while (count < maxSize && cin >> students[count].lastName >> students[count].firstName >> students[count].gpa) {
        count++;
    }
    return count;
}

3. Implement a Custom Sort Function #

Since we can't use library sorting functions (like std::sort), let's go with a bubble sort—it's straightforward and efficient enough for 50 elements. The sorting priority is:

• First compare lastName lexicographically
• If last names are identical, compare firstName lexicographically

void sortStudents(Student students[], int count) {
    for (int i = 0; i < count - 1; i++) {
        for (int j = 0; j < count - i - 1; j++) {
            // Swap if current student's last name comes after the next one
            if (students[j].lastName > students[j+1].lastName) {
                Student temp = students[j];
                students[j] = students[j+1];
                students[j+1] = temp;
            }
            // If last names match, compare first names
            else if (students[j].lastName == students[j+1].lastName) {
                if (students[j].firstName > students[j+1].firstName) {
                    Student temp = students[j];
                    students[j] = students[j+1];
                    students[j+1] = temp;
                }
            }
        }
    }
}

4. Output the Sorted Students #

Finally, we'll print each student's details in the sorted order:

void printStudents(Student students[], int count) {
    for (int i = 0; i < count; i++) {
        cout << students[i].lastName << " " << students[i].firstName << " " << students[i].gpa << endl;
    }
}

Full Main Function #

Putting all pieces together in the main function:

int main() {
    const int MAX_STUDENTS = 50;
    Student students[MAX_STUDENTS];
    int studentCount = readStudents(students, MAX_STUDENTS);
    
    sortStudents(students, studentCount);
    printStudents(students, studentCount);
    
    return 0;
}

Testing with Your Sample Input #

If you input:

Ware Henry 87.2 Dantes Edmond 91.4 Earhart Amelia 92.6

The program will output:

Dantes Edmond 91.4
Earhart Amelia 92.6
Ware Henry 87.2

Key Notes #

• Lexicographical Comparison: We use std::string's built-in comparison operators, which handle dictionary-style ordering exactly as needed for names.
• Input Robustness: The readStudents function automatically stops when there's no more input or we hit the 50-student limit, so it works with any valid input size under the cap.
• Sorting Choice: Bubble sort is perfect here—no need for a more complex algorithm like quicksort when dealing with only 50 elements.

内容的提问来源于stack exchange，提问作者samh30