// Preister, Joshua
// 7/21/2021
// This is a program demonstrating the statistics of Monty Hall's Problem
// for STAT380
// 

#include<iostream>
#include<ctime>
#include<cstdlib>
#include<string>


using namespace std;



int random(int upper, int lower){

    int number = rand() % upper + lower;

    return number;
}

int main(){

    int guess;
    int switchGuess = 0;
    int carDoor = rand() % 3 + 1;
    int showDoor = 0;
    string switchAnswer = "";

    double totalWon;

   cout << "Welcome to the Monty Hall Program. Please enter in what door you guess (1,2,3) : ";
   cin >> guess;

    if(guess > 3 || guess < 1){
        cout << "Invlaid Number, must be between 1-3. Try again.";
        return 0;
    }

    if(carDoor != 1 || guess != 1){
        showDoor = 1;
    } else if(carDoor != 2 || guess != 2){
        showDoor = 2;
    } else {
        showDoor = 3;
    }

    cout << "Door " << showDoor << " has a goat behind it. Will you switch?(\"Yes\" or \"No\"): ";
    cin >> switchAnswer;

    if(switchAnswer == "Yes"){
        while(switchGuess != 0 && switchGuess != showDoor && switchGuess != guess){
            guess = rand() % 3 + 1;
        }
        cout << "The car was behind door " << carDoor << ". The door you picked was door " << switchGuess << "." << endl;
        if(switchGuess == carDoor){
            cout << "You were correct!" << endl;
        } else{
            cout << "You were wrong." <<endl;
        }
    }else if(switchAnswer == "No"){
        cout << "The car was behind door " << carDoor << ". The door you picked was door " << guess << " ." << endl;
        if(guess == carDoor){
            cout << "You were correct!" << endl;
        }else{
            cout << "You were wrong." <<endl;
        }
    }

    cout << "Now, the program will run 1000 times using your user input and print the results" << endl << " to proove the 1/3 vs 2/3 odds and why it is benificial to switch when given the option. ";

    for(int i = 0; i <= 1000; i++){

        carDoor = rand() % 3 + 1;

        if(carDoor != 1 || guess != 1){
            showDoor = 1;
        } else if(carDoor != 2 || guess != 2){
            showDoor = 2;
        } else {
            showDoor = 3;
        }

        if(guess == carDoor){
            totalWon++;
        }
    }

    cout << "You won " << (100*(totalWon / 1000))  << "% of the time, and lost  " << 100 - (100*(totalWon / 1000)) << "% of the time." << endl;
    cout << "IMPORTANT TO NOTE: C++'s rand() isn't really random causing not an exact 1/3 - 2/3 split.";

 return 0;
}

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Read inputs from stdin

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#include <iostream>
#include <string>
using namespace std;

int main() 
{
    string name;
    cout << "Enter name:";
    getline (cin, name);
    cout << "Hello " << name;
    return 0;
}

About C++

C++ is a widely used middle-level programming language.

  • Supports different platforms like Windows, various Linux flavours, MacOS etc
  • C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
  • Case-sensitive
  • C++ is a compiler based language
  • C++ supports structured programming language
  • C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
  • Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition);

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}