main.cpp

#include <iostream>
#include <iomanip>
#include <string>
#include <cctype>
#include <limits>

using namespace std;

// Convert letter grade into grade point
double getGradePoint(string grade) {
    for (char &c : grade) {
        c = toupper(c);
    }

    if (grade == "A")  return 4.0;
    if (grade == "B+") return 3.5;
    if (grade == "B")  return 3.0;
    if (grade == "C+") return 2.5;
    if (grade == "C")  return 2.0;
    if (grade == "D")  return 1.0;
    if (grade == "F")  return 0.0;

    return -1.0;
}

int main() {

    int courses;

    cout << "============================================\n";
    cout << "          CODEALPHA CGPA CALCULATOR         \n";
    cout << "============================================\n\n";

    // Input number of courses
    while (true) {
        cout << "Enter number of courses: ";

        if (cin >> courses && courses > 0) {
            break;
        }

        cout << "Invalid input! Please enter a positive number.\n";
        cin.clear();
        cin.ignore(numeric_limits<streamsize>::max(), '\n');
    }

    string courseName;
    string grade;

    double creditHours;
    double totalCredits = 0.0;
    double totalQualityPoints = 0.0;

    cout << "\n--------------------------------------------\n";

    // Input course information
    for (int i = 1; i <= courses; i++) {

        cout << "\nCourse " << i << endl;

        cin.ignore(numeric_limits<streamsize>::max(), '\n');

        cout << "Enter course name: ";
        getline(cin, courseName);

        // Credit hour validation
        while (true) {
            cout << "Enter credit hours: ";

            if (cin >> creditHours && creditHours > 0) {
                break;
            }

            cout << "Invalid credit hours! Try again.\n";
            cin.clear();
            cin.ignore(numeric_limits<streamsize>::max(), '\n');
        }

        // Grade validation
        double gradePoint;

        while (true) {
            cout << "Enter grade (A, B+, B, C+, C, D, F): ";
            cin >> grade;

            gradePoint = getGradePoint(grade);

            if (gradePoint >= 0) {
                break;
            }

            cout << "Invalid grade! Please enter a valid grade.\n";
        }

        double qualityPoints = gradePoint * creditHours;

        totalCredits += creditHours;
        totalQualityPoints += qualityPoints;
    }

    // Calculate GPA
    double gpa = totalQualityPoints / totalCredits;

    // Display result
    cout << "\n\n============================================\n";
    cout << "               CGPA RESULT                 \n";
    cout << "============================================\n";

    cout << fixed << setprecision(2);

    cout << "Total Credit Hours : " << totalCredits << endl;
    cout << "Total Grade Points : " << totalQualityPoints << endl;
    cout << "GPA / CGPA         : " << gpa << endl;

    cout << "============================================\n";

    if (gpa >= 3.5) {
        cout << "Performance        : Excellent\n";
    }
    else if (gpa >= 3.0) {
        cout << "Performance        : Very Good\n";
    }
    else if (gpa >= 2.5) {
        cout << "Performance        : Good\n";
    }
    else if (gpa >= 2.0) {
        cout << "Performance        : Satisfactory\n";
    }
    else {
        cout << "Performance        : Needs Improvement\n";
    }

    cout << "============================================\n";

    return 0;
}