程序编译，但我认为开关被忽略

我目前正在学习C ，但我落后了一点，所以如果我的问题很明显，我深表歉意。

我必须创建一个程序，该程序要求学生的名字，GPA，入学年份，并为该人生成一个随机的5位数字。学生人数不会超过42。

我的程序编译（某种程度上），我能够获得无效菜单选择的错误，但是，每当我提供有效的选择（当前1）时，什么也不会发生。

也许我缺少一些东西，这就是为什么我需要帮助的原因。

这是我的代码。

#include <iostream>
#include <stdlib.h>
#include <time.h>
using namespace std;


//print all the menu options
void print_menu()
{
    cout<<"nRCNJ Registrar Menu:"<<"n"
        <<"n"
        <<"[1] Add a student"<<"n"
        <<"[2] Display all students"<<"n"
        <<"[3] Display by year"<<"n"
        <<"[4] Display statistics"<<"n"
        <<"[5] Quit"<<"n";
}

//get and return the student's name
void get_name(string& student_name) //call student_name after that.
{
    cout<<"Please enter the sudent's name: ";
    cin >> student_name;
    cout<<"n";
}
//validate and return gpa
double get_gpa()
{
    double student_gpa = 0;
        cout<<"Please enter the GPA: ";
        cin >>student_gpa;
        cout<<"n";
            while (student_gpa > 4 || student_gpa < 0)
            {
                cout<<"Please enter a valid GPA for the student (0.00 - 4.00): ";
                cin >> student_gpa;
                cout<<"n";
            }   
    return student_gpa;
}
//validateand return year
int get_year()
{
    int student_year = 0;
    cout<<"Please enter the year: ";
    cin >> student_year;
    cout<<"n";
        while (student_year >2016 || student_year <1972)
        {
            cout<<"Please enter a valid year (min 1972, max 2016): ";
            cin >> student_year;
            cout<<"n";
        }   
    return student_year;    
}
//generate the student's R#
int generate_number()
{
    int r_number;
        srand (time(NULL));
        r_number = rand() % 89999 + 10000;
    return r_number;
}

//save info. Include get_name, get_gpa, get_year
void input_new_student()
{
    string student_name;
    double student_gpa;
    int student_year;
    int r_number;
    int s_name, s_gpa, s_year, r_num;

    get_name(student_name);
    get_gpa();
    get_year();
    generate_number();

}

//display all students in the proper format
void print_all()
{
}
//get a year as selection and print all students that are the same year
void print_by_year()
{
}

//display statistics based on entered students
void print_statistics()
{
}
//validate and return the menu option selected by the user. 
//it should call print_menu defined earlier
int get_selection(int menu_choice)
{
    menu_choice = 0;
    cout<<"n"
        <<"Selection: ";
    cin >> menu_choice;
    cout<<"n";
        while (menu_choice > 5 || menu_choice< 1)
        {
            cout<<" Menu choice is invalid. Please re-enter (1 - 5): ";
            cin>> menu_choice;
            cout<<"n";
        }   
    return menu_choice;
}

int main()
{
    string student_name;
    double student_gpa;
    int student_year;
    int r_number;
    int menu_choice;
    int s_name=0;
    int s_gpa=0;
    int s_year=0;
    int r_num=0;
                string nameArray[42];
            s_name++;
            double gpaArray[42];
            s_gpa++;
            int yearArray[42];
            s_year++;
            int ramapoArray[42];
            r_num++;
        print_menu();
        get_selection(menu_choice);
            switch (menu_choice)
            {
                case 1: 
                input_new_student();
                nameArray[s_name] = student_name;
                gpaArray[s_gpa] = student_gpa;
                yearArray[s_year] = student_year;
                ramapoArray[r_num] = r_number;
                break;
            }



return 0;
}