Probability

[Stilmatz]

Hi,

I just wanted to know if there is ne way to put probability logic into a simple program. Basically i have written a program that tries to predict wat the user chooses between heads and tails. at the moment i am using Math.random() to predict the computers choice so is there ne way of storing say the last three choices (e.g H, H, T) and then making a decision of what to choice so the next choice for the computer should be programmed to choose a Head.

this is what i have written so far :
The Bit i want modified is bold and underlined,

would appreciate ne suggestions

public class MindReaderProgram {

	public static final int HEADS = 1;
	public static final int TAILS = 2;
	public static final int QUIT = 3;
	int iWon = 0;
	int youWon = 0;
	int totalTimesPlayed = 0;

	public void start() {
		String usersName = getUsersName();
		boolean userWantsToPlay = true;

		while (userWantsToPlay) {
			showUserChoices();
			showScores();
			int userChoice = getUserChoice();
			userWantsToPlay = userChoice != QUIT;
			if (userWantsToPlay) {
				int computerChoice = getComputerChoice();
				displayPlayerChoice(usersName, userChoice);
				displayPlayerChoice("I", computerChoice);
				String winnerString = workOutWinner(userChoice, computerChoice, usersName);
				displayWinner(winnerString);
			}
		}
		displayGoodbyeMessage(usersName);
	}

	private String getUsersName() {
		System.out.print("Hi!  What is your name? ");
		String name = Keyboard.readInput();
		System.out.println(name + " I will now attempt to read your mind!, choose either Heads or Tails: ");
		System.out.println();
		return name;
	}

	private void showUserChoices() {
		System.out.println(HEADS + ". HEADS");
		System.out.println(TAILS + ". TAILS");
		System.out.println(QUIT + ". Quit");
		System.out.println();
	}

	private void showScores() {
		System.out.println ("I have Won so far: " + iWon);
		System.out.println ("You have Won so far: " + youWon);
		System.out.println ("Number of times played so far: " + totalTimesPlayed);
	}
	private int getUserChoice() {
	   System.out.print("  Enter choice: ");
	   String userString = Keyboard.readInput();

	   userString = userString.trim();
	   System.out.println();
	   return Integer.parseInt(userString);
	}

	private int getComputerChoice() {
		if (totalTimesPlayed > 2 && (computerChoice == userChoice)) {
			return (!computerChoice);

		return (int) (Math.random() * 2 + 1);
	}

	private String workOutWinner(int userChoice, int computerChoice, String usersName) {
		String winnerString = " ";

		if (userChoice == computerChoice) {
			winnerString = "  I";
		} else if (!(userChoice == computerChoice)) {
			winnerString = " " + usersName;
		}
		winnerString = winnerString + " win because " + getResultString(userChoice, computerChoice);
		return winnerString;
	}

	private void displayWinner(String winner) {
		System.out.println(winner);
		System.out.println();
	}

	private void displayGoodbyeMessage(String name) {
		System.out.println("Goodbye " + name + ". Thanks for playing :)");
	}



//************************** Ex 1a ******************************

	private void displayPlayerChoice(String player, int choice) {
		if(choice == HEADS) {
			System.out.println(player + " chose Heads");
		}else if (choice == TAILS) {
			System.out.println(player + " chose Tails");
		}

	}

//************************** Ex 1b ******************************

	private boolean userWins(int userChoice, int computerChoice) {
		if (userChoice == HEADS && computerChoice == HEADS ){
			return true;

		}
		if (userChoice == TAILS && computerChoice == TAILS){
			return true;
		}

		return false;
	}

//************************** Ex 1c ******************************

	private String getResultString(int choice1, int choice2) {

		final String YOU_WINS = "OKAY, MAYBE I CAN'T READ MINDS";
		final String COMPUTER_WINS = "I READ YOUR MIND!";

		if(choice1 == choice2) {
			iWon++;
			totalTimesPlayed++;
			return COMPUTER_WINS;
		}
		if (choice1 == HEADS && choice2 == TAILS ) {
			youWon++;
			totalTimesPlayed++;
			return YOU_WINS;
		}
		if (choice1 == TAILS && choice2 == HEADS) {
			youWon++;
			totalTimesPlayed++;
			return YOU_WINS;
		}

		return ""; // Replace this whole line with your own lines of code.

	}
}

[WingedPanther]

I would store a list of the computer's guesses and the user's choices. I would keep a complete list, and try some pattern analysis on it. The simplest would be "if the user has done more heads than tails, guess tails" and vice-versa.

[Stilmatz]

yup but how do i write that in code ???

[bobdark]

You can hold two variables (counters) - one for heads and one for tails. Each time you increase the proper variable, and guess the one with the lower counts. Another possible option is to hold one variable - if you get head, you increase the counter by one and if you get tails, you DEcrease it by one. If the value is positive, guess tails, otherwise guess heads.

[WingedPanther]

You could store it in a list.