Write a Java program that implements Conway’s Game of Life, a simple cellular au
ID: 3763901 • Letter: W
Question
Write a Java program that implements Conway’s Game of Life, a simple cellular automaton.
The grid is represented by a 10 x 10 2dimensional integer array. If the grid point (i, j) is “populated”, the array element [i][j] contains 1; otherwise it contains 0. Elements along the edges, i == 0 or 9, or j == 0 or 9, are always unpopulated.
When we display the grid, a populated cell is indicated by a ‘#’; an unpopulated cell is indicated by a space.
What your program should do:
• Prompt the user to enter a list of (i,j) pairs, both nonnegative integers (stop when a negative integer is read for either i or j)
Prompt the user to enter the number of time steps
Initialize the grid based on the (i,j) pairs entered by the user (set the
corresponding array elements to 1)
Display the initial state of the grid (call the displayGrid() method)
For each time step,
update the grid according to Conway’s rules (call the updateGrid() method)
display the grid (call the displayGrid() method)
We follow Conway’s standard rules for updating the cells, as follows. A “neighbor” is a vertically, horizontally, or diagonally adjacent cell that is populated. A cell has anywhere from 0 to 8 neighbors.
For a cell that is “populated”, if the cell has <= 1 neighbors, or >= 4 neighbors, it dies (becomes 0). Otherwise, it survives (remains 1).
For a cell that is not populated, if the cell has exactly 3 neighbors, it becomes populated (becomes 1).
Cells on the edge always remain unpopulated (0). The displayGrid() method has prototype:
It displays the borders of the grid (see sample runs below), and prints the 10 x 10 grid of cells. Populated cells are indicated with a ‘#’ sign, unpopulated cells with a space.
The updateGrid() method has prototype:
mat is the 2dimensional array that contains the current state of the grid. The method counts the neighbors in each cell of the grid, and updates the cells in the grid according to Conway’s rules.
You can obviously enter arbitrary initial conditions to test your program. Some fun examples adapted from the bitstorm.org site:
Glider: initial populated cells at (3, 4) (4, 2) (4, 4) (5, 3) (5, 4)
5 cell row: initial populated cells at (6,4) (6,5) (6,6) (6,7) (6,8)
Small explosion: initial populated cells at (4, 5) (4,6) (5,4) (5,5) (5, 7) (6, 5) (6,6)
Note that these will not behave exactly the same as the bitstorm.org display when the populated cells run into the boundary conditions.
Explanation / Answer
Cell.java
class Cell
{
public Point Position
{
get;
private set;
}
public Rectangle Bounds
{
get;
private set;
}
public bool IsAlive
{
get;
set;
}
public Cell(Point position)
{
Position = position;
Bounds = new Rectangle(Position.X * Game1.CellSize, Position.Y * Game1.CellSize, Game1.CellSize, Game1.CellSize);
IsAlive = false;
}
public void Update(MouseState mouseState)
{
if (Bounds.Contains(new Point(mouseState.X, mouseState.Y)))
{
if (mouseState.LeftButton == ButtonState.Pressed)
IsAlive = true;
else if (mouseState.RightButton == ButtonState.Pressed)
IsAlive = false;
}
}
public void Draw(SpriteBatch spriteBatch)
{
if (IsAlive)
spriteBatch.Draw(Game1.Pixel, Bounds, Color.Black);
}
}
Grid.Java
class Grid
{
public Point Size { get; private set; }
private Cell[,] cells;
public Grid()
{
Size = new Point(Game1.CellsX, Game1.CellsY);
cells = new Cell[Size.X, Size.Y];
for (int i = 0; i < Size.X; i++)
for (int j = 0; j < Size.Y; j++)
cells[i, j] = new Cell(new Point(i, j));
}
public void Update(GameTime gameTime)
{
for (int i = 0; i < Size.X; i++)
{
for (int j = 0; j < Size.Y; j++)
{
bool living = cells[i, j].IsAlive;
int count = GetLivingNeighbors(i, j);
bool result = false;
if (living && count < 2)
result = false;
if (living && (count == 2 || count == 3))
result = true;
if (living && count > 3)
result = false;
if (!living && count == 3)
result = true;
cells[i, j].IsAlive = result;
}
}
}
public int GetLivingNeighbors(int x, int y)
{
int count = 0;
if (x != Size.X - 1)
if (cells[x + 1, y].IsAlive)
count++;
if (x != Size.X - 1 && y != Size.Y - 1)
if (cells[x + 1, y + 1].IsAlive)
count++;
if (y != Size.Y - 1)
if (cells[x, y + 1].IsAlive)
count++;
if (x != 0 && y != Size.Y - 1)
if (cells[x - 1, y + 1].IsAlive)
count++;
if (x != 0)
if (cells[x - 1, y].IsAlive)
count++;
if (x != 0 && y != 0)
if (cells[x - 1, y - 1].IsAlive)
count++;
if (y != 0)
if (cells[x, y - 1].IsAlive)
count++;
if (x != Size.X - 1 && y != 0)
if (cells[x + 1, y - 1].IsAlive)
count++;
return count;
}
public void SetNextState()
{
for (int i = 0; i < Size.X; i++)
for (int j = 0; j < Size.Y; j++)
cells[i, j].IsAlive = nextCellStates[i, j];
}
public void Draw(SpriteBatch spriteBatch)
{
foreach (Cell cell in cells)
cell.Draw(spriteBatch);
for (int i = 0; i < Size.X; i++)
spriteBatch.Draw(Game1.Pixel, new Rectangle(i * Game1.CellSize - 1, 0, 1, Size.Y * Game1.CellSize), Color.DarkGray);
for (int j = 0; j < Size.Y; j++)
spriteBatch.Draw(Game1.Pixel, new Rectangle(0, j * Game1.CellSize - 1, Size.X * Game1.CellSize, 1), Color.DarkGray);
}
protected override void Update(GameTime gameTime)
{
keyboardState = Keyboard.GetState();
if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
this.Exit();
if (keyboardState.IsKeyDown(Keys.Space) && lastKeyboardState.IsKeyUp(Keys.Space))
Paused = !Paused;
if (keyboardState.IsKeyDown(Keys.Back) && lastKeyboardState.IsKeyUp(Keys.Back))
grid.Clear();
base.Update(gameTime);
grid.Update(gameTime);
lastKeyboardState = keyboardState;
}
protected override void Draw(GameTime gameTime)
{
if (Paused)
GraphicsDevice.Clear(Color.Red);
else
GraphicsDevice.Clear(Color.White);
spriteBatch.Begin();
if (Paused)
{
string paused = "Paused";
spriteBatch.DrawString(Font, paused, ScreenSize / 2, Color.Gray, 0f, Font.MeasureString(paused) / 2, 1f, SpriteEffects.None, 0f);
}
grid.Draw(spriteBatch);
spriteBatch.End();
base.Draw(gameTime);
}
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