import java.util.Random; import java.util.ArrayList; public class MontyHall { //

Question

 import java.util.Random; import java.util.ArrayList;  public class MontyHall {  // First, write a function called simulate_prizedoor. // This function will simulate the location of the prize in many games -- see the detailed specification below: // //    Function //    -------- //    simulate_prizedoor // //    Generate a random array of 0s, 1s, and 2s, representing //    hiding a prize between door 0, door 1, and door 2 // //    Parameters //    ---------- //    nsim : int //    The number of simulations to run // //    Returns //    ------- //    sims : ArrayList //    Random ArrayList of 0s, 1s, and 2s //     static ArrayList<Integer> simulate_prizedoor(int nsim) {         // COMPLETE THIS PART      }  // Next, write a function that simulates the contestant's guesses for nsim simulations. // Call this function simulate_guess. The specs: // //    Function //    -------- //    simulate_guess // //    Return any strategy for guessing which door a prize is behind. This //    could be a random strategy, one that always guesses 2, whatever. // //    Parameters //    ---------- //    nsim : int //    The number of simulations to generate guesses for // //    Returns //    ------- //    guesses : ArrayList //    An ArrayList of guesses. Each guess is a 0, 1, or 2 //     static ArrayList<Integer> simulate_guess(int nsim) {         // COMPLETE THIS PART      }  // Next, write a function, goat_door, to simulate randomly revealing one of the goat doors // that a contestant didn't pick. // //    Function //    -------- //    goat_door // //    Simulate the opening of a "goat door" that doesn't contain the prize, //    and is different from the contestants guess // //    Parameters //    ---------- //    prizedoors : ArrayList //    The door that the prize is behind in each simulation //    guesses : ArrayList //    THe door that the contestant guessed in each simulation // //    Returns //    ------- //    goats : ArrayList //    The goat door that is opened for each simulation. Each item is 0, 1, or 2, and is different //    from both prizedoors and guesses //     static ArrayList<Integer> goat_door(ArrayList<Integer> prizedoors, ArrayList<Integer> guesses) {          // COMPLETE THIS PART       }  // Write a function, switch_guess, that represents the strategy of always switching a guess after the goat door is opened. // //    Function //    -------- //    switch_guess // //    The strategy that always switches a guess after the goat door is opened // //    Parameters //    ---------- //    guesses : ArrayList //    Array of original guesses, for each simulation //    goatdoors : ArrayList //    Array of revealed goat doors for each simulation // //    Returns //    ------- //    The new door after switching. Should be different from both guesses and goatdoors //     static ArrayList<Integer> switch_guess(ArrayList<Integer> guesses, ArrayList<Integer> goatdoors) {          // COMPLETE THIS PART       }  // Last function: write a win_percentage function that takes an array of guesses and prizedoors, // and returns the percent of correct guesses // //    Function //    -------- //    win_percentage // //    Calculate the percent of times that a simulation of guesses is correct // //    Parameters //    ----------- //    guesses : ArrayList //    Guesses for each simulation //    prizedoors : ArrayList //    Location of prize for each simulation // //    Returns //    -------- //    percentage : number between 0 and 100 //    The win percentage //     static double win_percentage(ArrayList<Integer> guesses, ArrayList<Integer> prizedoors) {          // COMPLETE THIS PART       }      public static void main(String[] Args) {         int number_of_trials = 10;          // DO NOT MAKE CHANGES TO THE MAIN FILE         ArrayList<Integer> prize = simulate_prizedoor(number_of_trials);         System.out.println(prize);          ArrayList<Integer> guess = simulate_guess(number_of_trials);         System.out.println(guess);                  ArrayList<Integer> goat = goat_door(prize, guess);         System.out.println(goat);                  ArrayList<Integer> new_door = switch_guess(guess, goat);         System.out.println(new_door);          System.out.println(" Win Percentage when not changing the door: " + win_percentage(guess, prize));         System.out.println(" Win Percentage after changing the door: " + win_percentage(new_door, prize));         // DO NOT MAKE CHANGES TO THE MAIN FILE     }    } 

Explanation / Answer

import java.util.Random;
import java.util.ArrayList;

public class MontyHall {

// First, write a function called simulate_prizedoor.
// This function will simulate the location of the prize in many games -- see the detailed specification below:
//
// Function
// --------
// simulate_prizedoor
//
// Generate a random array of 0s, 1s, and 2s, representing
// hiding a prize between door 0, door 1, and door 2
//
// Parameters
// ----------
// nsim : int
// The number of simulations to run
//
// Returns
// -------
// sims : ArrayList
// Random ArrayList of 0s, 1s, and 2s
//
static ArrayList<Integer> simulate_prizedoor(int nsim) {
// COMPLETE THIS PART
   ArrayList<Integer> randomList = new ArrayList<>();
   Random randomGenerator = new Random();
for (int i = 0; i < nsim; i++){
int randomInt = randomGenerator.nextInt(3);
randomList.add(randomInt);
}
return randomList;
}

// Next, write a function that simulates the contestant's guesses for nsim simulations.
// Call this function simulate_guess. The specs:
//
// Function
// --------
// simulate_guess
//
// Return any strategy for guessing which door a prize is behind. This
// could be a random strategy, one that always guesses 2, whatever.
//
// Parameters
// ----------
// nsim : int
// The number of simulations to generate guesses for
//
// Returns
// -------
// guesses : ArrayList
// An ArrayList of guesses. Each guess is a 0, 1, or 2
//
static ArrayList<Integer> simulate_guess(int nsim) {
// COMPLETE THIS PART
   ArrayList<Integer> guess = new ArrayList<>();
   Random randomGenerator = new Random();
   for (int i = 0; i < nsim; i++){
       int randomInt = randomGenerator.nextInt(3);
       guess.add(randomInt);
   }
   return guess;
}

// Next, write a function, goat_door, to simulate randomly revealing one of the goat doors
// that a contestant didn't pick.
//
// Function
// --------
// goat_door
//
// Simulate the opening of a "goat door" that doesn't contain the prize,
// and is different from the contestants guess
//
// Parameters
// ----------
// prizedoors : ArrayList
// The door that the prize is behind in each simulation
// guesses : ArrayList
// THe door that the contestant guessed in each simulation
//
// Returns
// -------
// goats : ArrayList
// The goat door that is opened for each simulation. Each item is 0, 1, or 2, and is different
// from both prizedoors and guesses
//
static ArrayList<Integer> goat_door(ArrayList<Integer> prizedoors, ArrayList<Integer> guesses) {

// COMPLETE THIS PART
   ArrayList<Integer> goat_door = new ArrayList<>();
   int j=0;
   for (Integer i : prizedoors) {
       if(i != guesses.get(j))
           goat_door.add(3-i-guesses.get(j));
       else if(i == 0)
           goat_door.add(1);
       else
           goat_door.add(3-i);
          
       j++;
       }
  
   return goat_door;

}

// Write a function, switch_guess, that represents the strategy of always switching a guess after the goat door is opened.
//
// Function
// --------
// switch_guess
//
// The strategy that always switches a guess after the goat door is opened
//
// Parameters
// ----------
// guesses : ArrayList
// Array of original guesses, for each simulation
// goatdoors : ArrayList
// Array of revealed goat doors for each simulation
//
// Returns
// -------
// The new door after switching. Should be different from both guesses and goatdoors
//
static ArrayList<Integer> switch_guess(ArrayList<Integer> guesses, ArrayList<Integer> goatdoors) {

// COMPLETE THIS PART

   ArrayList<Integer> switch_guess = new ArrayList<>();
   int j=0;
   for (Integer i : goatdoors) {
       if(i != guesses.get(j))
           switch_guess.add(3-i-guesses.get(j));
       else if(i == 0)
           switch_guess.add(1);
       else
           switch_guess.add(3-i);
          
       j++;
       }
  
   return switch_guess;
}

// Last function: write a win_percentage function that takes an array of guesses and prizedoors,
// and returns the percent of correct guesses
//
// Function
// --------
// win_percentage
//
// Calculate the percent of times that a simulation of guesses is correct
//
// Parameters
// -----------
// guesses : ArrayList
// Guesses for each simulation
// prizedoors : ArrayList
// Location of prize for each simulation
//
// Returns
// --------
// percentage : number between 0 and 100
// The win percentage
//
static double win_percentage(ArrayList<Integer> guesses, ArrayList<Integer> prizedoors) {

// COMPLETE THIS PART
  
   int win = 0;
   int j=0;
   for (Integer i : prizedoors) {
       if (i==guesses.get(j))
           win++;
       j++;
       }
  
   return ((win*1.0)/j)*100.0;

}

public static void main(String[] Args) {
int number_of_trials = 10;

// DO NOT MAKE CHANGES TO THE MAIN FILE
ArrayList<Integer> prize = simulate_prizedoor(number_of_trials);
System.out.println(prize);

ArrayList<Integer> guess = simulate_guess(number_of_trials);
System.out.println(guess);
  
ArrayList<Integer> goat = goat_door(prize, guess);
System.out.println(goat);
  
ArrayList<Integer> new_door = switch_guess(guess, goat);
System.out.println(new_door);

System.out.println(" Win Percentage when not changing the door: " + win_percentage(guess, prize));
System.out.println(" Win Percentage after changing the door: " + win_percentage(new_door, prize));
// DO NOT MAKE CHANGES TO THE MAIN FILE
}

}

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