P6.6 The game of Nim. This is a well-known game with a number of variants. The f
ID: 3592301 • Letter: P
Question
P6.6 The game of Nim. This is a well-known game with a number of variants. The fol- lowing variant has an interesting winning strategy. Two players alternately take marbles from a pile. In each move, a player chooses how many marbles to take. The player must take at least one but at most half of the marbles. Then the other player takes a turn. The player who takes the last marble loses. Write a program in which the computer plays against a human opponent. Generate a random integer between 10 and 100 to denote the initial size of the pile. Generate a random integer between 0 and 1 to decide whether the computer or the human takes the first turn. Generate a random integer between 0 and 1 to decide whether the computer plays smart or stupid. In stupid mode the computer simply takes a random legal value (between 1 and n/2) from the pile whenever it has a turn. In smart mode the computer takes off enough marbles to make the size of the pile a power of two minus 1-that is, 3,7,15,31, or 63. That is always a legal move, except when the size of the pile is currently one less than a power of two. In that case, the computer makes a random legal move You will note that the computer cannot be beaten in smart mode when it has the first move, unless the pile size happens to be 15, 31, or 63. Of course, a human player who has the first turn and knows the winning strategy can win against the computer.Explanation / Answer
import java.util.Random;
public class Game
{
public static void main(String args[]) {
//declare variables
Pile marbles = new Pile();
Random random = new Random();
Player player1;
Player player2;
int marblesToRemove = 0; //determine who goes first
if(random.nextInt(2) == 0)
{
System.out.println("User goes first ");
player1 = new Player(2);
player2 = new Player();
}
else
{
System.out.println("Computer goes first ");
player1 = new Player();
player2 = new Player(2);
}
//keep going until all the marbles are gone
while(marbles.getMarbles() > 0)
{
//check if player two wins
if(marbles.getMarbles() == 1)
{
System.out.println("Player 2 Wins!!!");
break;
}
//prompt/calculate number of marbles to remove
System.out.println("Number of marbles left: " + marbles.getMarbles());
System.out.println("Player 1's turn:");
marblesToRemove = player1.chooseNextMove(marbles.getMarbles());
System.out.println("Player 1 removed " + marblesToRemove);
System.out.println();
//remove the marbles
marbles.removeMarbles(marblesToRemove);
//check if player one wins
if(marbles.getMarbles() == 1)
{
System.out.println("Player 1 Wins!!!");
break;
}
//prompt/calculate number of marbles to remove
System.out.println("Number of marbles left: " + marbles.getMarbles());
System.out.println("Player 2's turn:");
marblesToRemove = player2.chooseNextMove(marbles.getMarbles());
System.out.println("Player 2 removed " + marblesToRemove);
System.out.println();
//remove marbles
marbles.removeMarbles(marblesToRemove);
}
}
}
import java.util.Random;
public class Pile
{
//fields
int numMarbles = 0;
//generate the number of marbles
public Pile()
{
Random random = new Random();
numMarbles = random.nextInt(89) + 11;
}
//get method
public int getMarbles()
{
return numMarbles;
}
//remove method
public void removeMarbles(int marblesToRemove)
{
numMarbles -= marblesToRemove;
}
}
import java.util.Random;
import java.util.Scanner;
public class Player
{
int playerType = 0;
// 0 dumb, 1 smart, 2 player
Random random = new Random();
Scanner input;
//constructor where player type is specified
public Player(int type)
{
if (type < 0 || type > 2)
playerType = 2;
else
playerType = type;
input = new Scanner(System.in);
}
//constructor where player type is specified
public Player()
{
playerType = random.nextInt(2);
input = new Scanner(System.in);
}
//pick next move
public int chooseNextMove(int marblesLeft)
{
//setup variables
int marblesToRemove = 0;
//remove the second to last marble
if(marblesLeft == 3)
return 1;
//if dumb, pick random number
if(playerType == 0)
{
marblesToRemove = random.nextInt((marblesLeft/2) - 1) + 1;
}
//if smart get to specific numbers
else if (playerType == 1)
{
if(marblesLeft > 63)
marblesToRemove = marblesLeft - 63;
else if(marblesLeft > 31)
marblesToRemove = marblesLeft - 31;
else if(marblesLeft > 15)
marblesToRemove = marblesLeft - 15;
else if(marblesLeft > 7)
marblesToRemove = marblesLeft - 7;
else if(marblesLeft > 3)
marblesToRemove = marblesLeft - 3;
else if(marblesLeft == 2)
marblesToRemove = 1;
//pick random number
else
marblesToRemove = random.nextInt((marblesLeft/2) - 1 ) + 1;
}
else
{
//prompt user
System.out.println("Please enter a number of marbles to remove between 1 and " + (marblesLeft / 2));
marblesToRemove = input.nextInt();
//error check
while(marblesToRemove > marblesLeft / 2 || marblesToRemove < 0)
{
System.out.println("That is not a valid entry, please try again (1 - " + (marblesLeft / 2) + ")");
marblesToRemove = input.nextInt();
}
}
//return values
return marblesToRemove;
}
}
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