CSE 273 Assignment

NSUID.cpp

#include <iostream>
using namespace std;

int Check(string stdID);

int main(void)
{
    string stdID = "";
    while (true)
    {
        cout << "Please enter the student ID: ";
        cin >> stdID;
        if(stdID == "X" || stdID == "x")
        {
            cout << "Thank you for using the program!" << endl;
            break;
        }
        else
            Check(stdID);
    }

}

int Check(string stdID)
{
    /*
    string stdID;
    cout << "Please enter the student ID: ";
    cin >> stdID;
     */

    // 1. Check the length

    int len = stdID.length();
    if (len != 10)
    {
        cout << "Invalid student ID : length is wrong." << endl;
        return 0;
    }

    // 2. Check if all the characters are digits

    for (int i = 0; i < len; ++i)
    {
        if (!isdigit(stdID[i]))
        {
            cout << "Invalid student ID : all characters must be digits." << endl;
            return 0;
        }
    }

    // 3. Check the first character

    if (stdID[0] > '1')
    {
        cout << "Invalid student ID : invalid year." << endl; // Time traveller!
        return 0;
    }

    // 4. Deduct the year and check it

    int year = (stdID[0] - '0') * 10 + (stdID[1] - '0');

    if (year > 18) // Another time traveller!
    {
        cout << "Invalid student ID : invalid year." << endl;
        return 0;
    }
    else if (year == 18)
    {
        if (stdID[2] > '1') // Invalid semester for 2018
        {
            cout << "Invalid student ID : invalid semester." << endl;
            return 0;
        }
    }
    else
    {
        if(stdID[2] > '3') // A student admitted into a non-existent semester. Fishy 🤔
        {
            cout << "Invalid student ID : invalid semester." << endl;
            return 0;
        }
    }
    if (stdID[7] != '0' && stdID[7] != '6')
    {
        cout << "Invalid student ID : third last digit must be either 0 or 6." << endl;
        return 0;
    }

    cout << "Valid student ID." << endl;
    return 0;
}