#include <iostream>

using namespace std;
/*functions / methods */
//parameter
void welcome(); //declaration of function, procedure
bool isNumber(string);
void enterName();
double add(double a, double b) {return a + b;}
void changeValueTo10(int a)
{
  a = 10;
}
int main()
{
   // welcome();
   /* enterName();
    enterName();
    enterName();*/
    char ch;
    cout << "Do you want to end the program? (Y/N)" << endl;

    cin >> ch;
    if (ch == 'Y' || ch == 'y')
    return 0;
   // cout << add(4,5);
    int a = 5;

    changeValueTo10(a);

    cout << a;

    return 0;
}

void welcome()
{
    cout << "HEllo, welcome in my program!! :-)" << endl;
}
bool isNumber(string tmp)
{
    if (tmp[0] == '0')
        return false;
    for (int i = 0; i < tmp.length(); i++)
    {
        if (!(tmp[i] >= 48 && tmp[i] <= 57))
            return false;
    }

    return true;
}
void enterName()
{
    string tmp;

    cout << "Enter the number: " << endl;
    cin >> tmp; //124

    if (isNumber(tmp))
        cout << "Number entered properly " << endl;
    else
        cout << "Number wasn't entered properly " << endl;
}

#include <iostream>
#define PI 3.14
using namespace std;
// the belows are declaration of function
void initMenu();
void menuDecision(int);
double areaCircle(double);
double areaSquare(double);
double areaRectangle(double, double);
double areaTriangle(double, double);
int main()
{
    int choice;
    char cont;
    do
    {
        system("cls"); //clear screen = cls
        initMenu();

        cin >> choice;

        menuDecision(choice);

        do
        {
            cout << "Do you want to continue the program? (Y/N)" << endl;
            cin >> cont;
        } while(cont != 'y' && cont != 'Y' && cont != 'N' && cont != 'n');


    } while(cont == 'y' || cont == 'Y');

    return 0;
}
void initMenu()
{
    cout << "Enter option:" << endl;
    cout << "1. Circle" << endl;
    cout << "2. Square" << endl;
    cout << "3. Rectangle" << endl;
    cout << "4. Triangle" << endl;
}
void menuDecision(int choice)
{
    double r, a, b, h;
    switch(choice)
    {
        case 1:
            cout << "Enter the radius: " << endl;
            cin >> r;
            areaCircle(r);
            break;
        case 2:
            cout << "Enter the side of a square: " << endl;
            cin >> a;
            areaSquare(a);
            break;
        case 3:
            cout << "Enter the width and height of a rectangle: " << endl;
            cin >> a >> b;
            areaRectangle(a, b);
            break;
        case 4:
            cout << "Enter the base and height of a triangle: " << endl;
            cin >> a >> h;
            areaTriangle(a, h);
            break;
        default:
            cout << "You didn't choose any of the option from above" << endl;

    }
}
double areaCircle(double r)
{
    double result = PI * r * r;

    cout << "The area of a circle that radius is " << r << " = " << result << endl;

    return result;
}
double areaSquare(double a)
{
    double result = a * a;

    cout << "The area of a square that side is " << a << " = " << result << endl;

    return result;
}
double areaRectangle(double a, double b)
{
    double result = a * b;

    cout << "The area of a rectangle that first side is " << a << " the second side is " << b << " = " << result << endl;

    return result;
}
double areaTriangle(double a, double h)
{
    double result = (1/2.0) * a * h;

    cout << "The area of a rectangle that first side is " << a << " the second side is " << h << " = " << result << endl;

    return result;
}

#include <iostream>

using namespace std;

/* overloading functions */
int power(int, int);
double power(double, int);
int main()
{

    cout << power(2, 6) << endl;

    return 0;
}

/*
    2 ^ 3 = 2 * 2 * 2

    2 ^ 1 = 2
    2 ^ 2 = 4
    2 ^ 3 = 8
*/
int power(int b, int e) // b = 8, e = 1
{
    int tmp = b; //tmp = 2
    int i = 0;

    while(i++ < e)
    {
        cout << tmp << " ^ " << i << " = " << b << endl;
        if (i != e)
            b *= tmp; //b = b * tmp;
    }

    return b;
}
double power(double b, int e)
{
    double tmp = b; //tmp = 2
    while(e-- > 1)
        b *= tmp; //b = b * tmp;

    return b;
}

#include <iostream>

using namespace std;
/*scope / range of varables */

int globalVariable;

main()
{
    int localVariable;
/*
    cout << "value of globalVariable: " << globalVariable << endl;
    cout << "value of localVariable: " << localVariable << endl;
*/
    int a = 10;
/*
    if (a == 10)
    {
        int result = a * 10;
    }



    cout << result << endl;*/

    int nr, result = 0;
    int i = 0;
    for (; i < 3; i++) // 3,2,3 - will the result be 8??? NOOOOOOOOO, we have to assign 0 to the result!
    {
        cout << "Enter " << (i + 1) << " number" << endl;
        cin >> nr;
        result += nr; //result = result + nr;
    }

    cout << result << endl;
    cout << "we added " << i << " numbers" << endl;
}

#include <iostream>
#include <cstdlib>

using namespace std;

double minValue(double tab[]);
double maxValue(double tab[]);


int main ()
{
    double tab[5];

    for (int i = 0; i < 5; i++)
    {
        cout << "Input " << i+1 << " number: ";
        cin >> tab[i];
    }

    cout << "The minimum value was: " << minValue(tab) << endl;
    cout << "The maximum value was: " << maxValue(tab) << endl;

    return 0;
}

double minValue(double tab[])
{
    double minValue = tab[0];

    for (int i = 1; i < 5; i++)
    {
        if (minValue > tab[i])
            minValue = tab[i];

    }

    return minValue;
}
double maxValue(double tab[])
{
    double maxValue = tab[0];

    for (int i = 1; i < 5; i++)
    {
        if (maxValue < tab[i])
            maxValue = tab[i];

    }

    return maxValue;
}

#include <iostream>
#include <limits> // to make "cin.ignore(numeric_limits<streamsize>::max(), '\n');"r active
#define PI 3.14
using namespace std;
/*validating data
    buffer - temporary array
*/
void initMenu();
void menuDecision(int);
double areaCircle(double);
double areaSquare(double);
double areaRectangle(double, double);
double areaTriangle(double, double);
bool isValid(string);
bool isValid();
int main()
{
    int choice;
    char cont;
    do
    {
        system("cls"); //clear screen = cls
        initMenu();

        while(!(cin >> choice))
        {
            //cout << "state before: " << cin.rdstate() << endl;
            cin.clear();
            //cout << "state after: " << cin.rdstate() << endl;
            cin.ignore(numeric_limits<streamsize>::max(), '\n'); // skip the '\n' charcter left in the input buffer
            // 정수를 입력받은 후에 문자열을 입력받지 않고 다음 코드로 넘어간다. 버퍼에 정수값을 누른 엔터가 남아있어 그렇다. getline을 이용하기 위해서는 정수값을 입력받은뒤 ignore을 사용한다.

            system("cls");
            initMenu();
            cout << "You've just typed the wrong data to the input. " << endl;
        }

        menuDecision(choice);

        do
        {
            cout << "Do you want to continue the program? (Y/N)" << endl;
            cin >> cont; //asdfg
            cin.ignore(numeric_limits<streamsize>::max(), '\n');

        } while(cont != 'y' && cont != 'Y' && cont != 'N' && cont != 'n');


    } while(cont == 'y' || cont == 'Y');

    return 0;
}
void initMenu()
{
    cout << "Enter option:" << endl;
    cout << "1. Circle" << endl;
    cout << "2. Square" << endl;
    cout << "3. Rectangle" << endl;
    cout << "4. Triangle" << endl;
}
void menuDecision(int choice)
{
    double r, a, b, h;
    switch(choice)
    {
        case 1:

            do { cout << "Enter the radius: " << endl; cin >> r; } while(!isValid());
            areaCircle(r);
            break;
        case 2:
            cout << "Enter the side of a square: " << endl;
            do { cin >> a; } while(!isValid("The data is wrong, please type it again:"));
            areaSquare(a);
            break;
        case 3:
            cout << "Enter the width and height of a rectangle: " << endl;
            do { cin >> a >> b; } while(!isValid("The data is wrong, please type it again:"));
            areaRectangle(a, b);
            break;
        case 4:
            cout << "Enter the base and height of a triangle: " << endl;
            do { cin >> a >> h; } while(!isValid("The data is wrong, please type it again:"));
            areaTriangle(a, h);
            break;
        default:
            cout << "You didn't choose any of the option from above" << endl;

    }
}
double areaCircle(double r)
{
    double result = PI * r * r;

    cout << "The area of a circle that radius is " << r << " = " << result << endl;

    return result;
}
double areaSquare(double a)
{
    double result = a * a;

    cout << "The area of a square that side is " << a << " = " << result << endl;

    return result;
}
double areaRectangle(double a, double b)
{
    double result = a * b;

    cout << "The area of a rectangle that first side is " << a << " the second side is " << b << " = " << result << endl;

    return result;
}
double areaTriangle(double a, double h)
{
    double result = (1/2.0) * a * h;

    cout << "The area of a rectangle that first side is " << a << " the second side is " << h << " = " << result << endl;

    return result;
}
bool isValid(string error_msg)
{
    if (cin.rdstate()) //state is wrong when it is not equal to 0
    {
        cin.clear();
        cin.ignore(numeric_limits<streamsize>::max(), '\n');
        system("cls");
        initMenu();
        cout << error_msg << endl;
        return false;
    }

    return true;
}
bool isValid()
{
    if (cin.rdstate()) //state is wrong when it is not equal to 0 // state is not wrong when it is equal to 0
    {
        cin.clear();
        cin.ignore(numeric_limits<streamsize>::max(), '\n'); // skip the enter key left in the buffer
        system("cls");
        initMenu();
        return false;
    }

    return true;
}