Lesson - 04

• While
• Break
• Continue
• Do while
• Exception handling

Write a program to print only odd numbers using while loop

#include <iostream>

int main(int argc, char const *argv[])
{
    // create a variable to use in loop
    int i = 0;

    // printing the values
    while(i < 10){
        if(i % 2 == 0){
            i+= 1;
            continue;
        }

        std::cout << i << ", ";

        // increment the i
        i = i + 1;
    }

    return 0;
}

Write a program to draw pine tree on the screen.

// Sample Output: 
/*
    #
   ###
  #####
 #######
#########
    #
*/

#include <iostream>

int main(int argc, char const *argv[])
{
    // store height, spaces and hashes
    int height = 0;
    int spaces = 0;
    int hashes = 1;
    int tailSpaces = 0;

    // ask user height of tree
    std::cout << "Enter height of tree: ";
    std::cin >> height;

    // set the spaces and hashes
    spaces = height - 1;

    // just to put last space in center
    tailSpaces = spaces;

    // draw the tree
    while(height > 0){

        // draw the spaces
        // 4, 3, 2, 1, 0
        for(int i=0; i < spaces; ++i){
            std::cout << " ";
        }

        // decrement the spaces by 1
        spaces--;


        // draw the hashes
        // 1, 3, 5, 7, 9
        for(int i=0; i < hashes; ++i){
            std::cout << "#";
        }

        // increment the hashes by 2
        hashes += 2;

        // print a new line
        std::cout << "\n";

        // decrement the height
        height--;
    }

    // draw the tail of the tree
    for(int i=0; i<tailSpaces; ++i){
        std::cout << " ";
    }

    // draw the hash after spaces
    std::cout << "#" << std::endl;

    return 0;
}

Write a program to divide two numbers and handle the division by zero exception.

#include <iostream>

int main(int argc, char const *argv[])
{
    // declare two numbers
    double num1 = 0.0;
    double num2 = 1.0;

    // handle the zero division exception
    try{
        // ask user for input
        std::cout << "Enter First number: ";
        std::cin >> num1;

        std::cout << "Enter second number: ";
        std::cin >> num2;

        // check if num2 is zero
        if(num2 == 0) throw "Division by 0 is not possible.";

        // divide the numbers
        double result = num1 / num2;

        // print the result
        std::cout << "Result: " << num1 / num2 << std::endl;

    }catch(const char *ex){
        std::cout << "Error: " << ex << std::endl;
    }

    return 0;
}

Write a program to demonstrate that after an error is thrown the remaining code inside try block is not executed. Throw an runtime error. Also catch all other exceptions.

#include <iostream>

int main(int argc, char const *argv[])
{
    try{
        std::cout << "Throwing exception" << std::endl;
        throw std::runtime_error("Error Occured.");

        // the below statements will not execute
        std::cout << "The statement inside try." << std::endl;

    }catch(std::exception &exp){
        std::cout << "Handled Exception: " << exp.what() << std::endl;
    }
    catch(...){
        /// ... ellipsis will catch all exceptions.

        std::cout << "Default Exception:" << std::endl;
    }

    return 0;
}

Write a program to demonstrate do while loop and also generate random number using ctime module.

• Create a secret number guessing game.

ctime module will provide you with seconds passed till now since January 1, 1970

#include <iostream>
#include <ctime>

int main(int argc, char const *argv[])
{
    // create a seed
    srand(time(NULL));

    // create a secret num
    int secretNum = std::rand() % 10;

    // create a guess variable
    int guess = 0;

    do{
        // ask the user to enter a number
        std::cout << "Guess a number between 0 to 10: ";
        std::cin >> guess;

    }while(guess != secretNum);

    return 0;
}

Create a number guessing game using only while loop.

#include <iostream>
#include <ctime>

int main(int argc, char const *argv[])
{
    // seed the time to random function
    srand(time(NULL));

    // generate the random number.
    int random = std::rand() % 10;

    // store the guess
    int guess = 0;

    while(1){
        // ask the user for a input
        std::cout << "Guess a number: ";
        std::cin >> guess;

        // check if the guess is correct
        if(guess == random) break;
    }

    std::cout << "Hey, you guessed it right!" << std::endl;

    return 0;
}

Create a user login screen prompting user for username and password. Invalid password will make the user try again.

#include <iostream>

std::string USER_NAME = "root";
std::string PASSWORD = "root";

int main(int argc, char const *argv[])
{
    // store the username and password
    std::string username = "";
    std::string password = "";

    // ask the user for username and password
    do{


        // ask for username
        std::cout << "Enter your username: ";
        getline(std::cin, username);

        // ask for password
        std::cout << "Enter password: ";
        getline(std::cin, password);

        if(username == USER_NAME && password != PASSWORD){
            // clear the screen
            std::system("cls || clear");

            // tell the user for incorrect password
            std::cout << "=====================" << std::endl;
            std::cout << "   Invalid Password  " << std::endl;
            std::cout << "=====================" << std::endl;
        }


    }while((username != USER_NAME) || (password != PASSWORD));

    // clear the screen
    std::system("cls || clear");

    // print the auth success message.
    std::cout << "Authentication successful." << std::endl;

    return 0;
}