Game of Life Java Program

[namarino]

Hey guys, I have to program conway's game of life in Java, but I'm having a lot of trouble, I feel like a complete moron right now. This is what I have so far:

public GameOfLifeBoard(String file_name){		Scanner input;		String character;				try {			input = new Scanner(new File(file_name));			rows = input.nextInt();			columns = input.nextInt();						current = new boolean[rows][columns];						for(int x = 0; x < current.length; x++){				for(int y = 0; y < current[x].length; y++){					character = input.next();					if(character.equals("*")){						current[x][y] = true;					}				}			}		} catch (FileNotFoundException e) {			System.out.print("The file " + file_name + " could not be found.");		}	}

This just reads the file into the array current. Right now, I'm trying to figure out a way to implement the rules of the game in order to determine whether a cell lives or dies, but I can't think of any way to do it without having a mile long line of code inside an if statement (I would be checking every element around the element in question). Can someone help me with this? Thanks a lot!

[SSL]

"Have to program"? Why not start with something simpler?

[namarino]

"Have to program"? Why not start with something simpler?

School project

[79wjd]

School project

I might be able to help if you explain what you need help trying to do. (I don't remember the rules of life at all) 

[namarino]

I might be able to help if you explain what you need help trying to do. (I don't remember the rules of life at all) 

Ok so basically the rules are as follows: A cell survives if it has 2 or 3 neighbors. A cell dies if it has more than 3 neighbors or less than 2. A cell is born if it is adjacent to exactly 3 cells. So I have to find a way to implement those rules basically. I have to determine whether a cell lives or dies by looking at its surroundings. Does that make sense?? Maybe I didn't explain it very well. 

[SSL]

I might be able to help if you explain what you need help trying to do. (I don't remember the rules of life at all) 

 

Probably a lot of people around here can help, the issue is doing it without just writing the code for them.

[SSL]

Ok so basically the rules are as follows: A cell survives if it has 2 or 3 neighbors. A cell dies if it has more than 3 neighbors or less than 2. A cell is born if it is adjacent to exactly 3 cells. So I have to find a way to implement those rules basically. I have to determine whether a cell lives or dies by looking at its surroundings. Does that make sense?? Maybe I didn't explain it very well. 

 

What solution do you have so far? Even just in pseudocode/plain english?

[namarino]

Probably a lot of people around here can help, the issue is doing it without just writing the code for them.

Yeah I don't want the code, I just want someone to explain.

[namarino]

What solution do you have so far? Even just in pseudocode/plain english?

Ok so basically I have an if statement that says:

if(array[x-1][y-1] && array[x-1][y] || etc...)

 

You can see how long that will go on for...

[SSL]

Yeah I don't want the code, I just want someone to explain.

 

Well like I said, it helps to write out the steps in english first. E.g. "For each cell, check how many neighbors it has and store the value. If the number of neighbors is more than three..." and so on.

[namarino]

Well like I said, it helps to write out the steps in english first. E.g. "For each cell, check how many neighbors it has and store the value. If the number of neighbors is more than three..." and so on.

How can I check the number of neighbors in a more efficient way?

[SSL]

How can I check the number of neighbors in a more efficient way?

 

Instead of checking for every possible combination of two neighbors or more than three, just count the total numbers. You don't care which neighbors are there, right? Just how many there are. So possibly a loop of some kind, maybe in it's own function that returns a single value. That narrows down your if statements when you actually do the death check.

[TechFnatic]

Hey guys, I have to program conway's game of life in Java, but I'm having a lot of trouble, I feel like a complete moron right now. This is what I have so far:

public GameOfLifeBoard(String file_name){		Scanner input;		String character;				try {			input = new Scanner(new File(file_name));			rows = input.nextInt();			columns = input.nextInt();						current = new boolean[rows][columns];						for(int x = 0; x < current.length; x++){				for(int y = 0; y < current[x].length; y++){					character = input.next();					if(character.equals("*")){						current[x][y] = true;					}				}			}		} catch (FileNotFoundException e) {			System.out.print("The file " + file_name + " could not be found.");		}	}

This just reads the file into the array current. Right now, I'm trying to figure out a way to implement the rules of the game in order to determine whether a cell lives or dies, but I can't think of any way to do it without having a mile long line of code inside an if statement (I would be checking every element around the element in question). Can someone help me with this? Thanks a lot!

What course are you taking?

[namarino]

Instead of checking for every possible combination of two neighbors or more than three, just count the total numbers. You don't care which neighbors are there, right? Just how many there are. So possibly a loop of some kind, maybe in it's own function that returns a single value. That narrows down your if statements when you actually do the death check.

Oh so a for loop that loops around the cell in question? Ohhhhhh and then every time it passes a live cell, add 1 to some variable. Would that work?

[namarino]

What course are you taking?

Intro to Computer Science II. Why do you ask??

[SSL]

Oh so a for loop that loops around the cell in question? Ohhhhhh and then every time it passes a live cell, add 1 to some variable. Would that work?

 

Sure. A cell I assume can have at most eight neighbors, so there's your loop; you would return whatever that accumulator ended up at the end.

[namarino]

Sure. A cell I assume can have at most eight neighbors, so there's your loop; you would return whatever that accumulator ended up at the end.

Ok got it. Let me try to code that real quick and I'll let you know if it works.

[namarino]

Sure. A cell I assume can have at most eight neighbors, so there's your loop; you would return whatever that accumulator ended up at the end.

Ok so I'm not sure how good stylistically this is, but it works! haha You feed it the coordinates of the cell in questions and it returns the number of surrounding live cells.

public int neighbours(int row, int column){		int neighbours = 0;				for(int x = (row - 1); x < (row + 2); x++){			for(int y = (column - 1); y < (column + 2); y++){				if(current[x][y]){					neighbours++;				}				if(x == row && y == column){					neighbours--;				}			}		}		return neighbours;		}

[SSL]

Ok so I'm not sure how good stylistically this is, but it works! haha You feed it the coordinates of the cell in questions and it returns the number of surrounding live cells.

 

That's the ticket. Of course there are a number of ways of doing it in the code but the result should be the same.

[fizzlesticks]

A loop might not be the best idea since each cell is going to have different out of bounds conditions.

Also in your current code the current cell might not be true so doing 

if(x == row && y == column){    neighbours--;}

may end up with an off by 1 error.

[namarino]

A loop might not be the best idea since each cell is going to have different out of bounds conditions.

Also in your current code the current cell might not be true so doing 

if(x == row && y == column){    neighbours--;}

may end up with an off by 1 error.

 

That's the ticket. Of course there are a number of ways of doing it in the code but the result should be the same.

I think a loop is probably the best way to do it. Do you have any other suggestions? 

[fizzlesticks]

I think a loop is probably the best way to do it. Do you have any other suggestions? 

If you want to stick with a loop you could either get the minimum and maximum row and column before looping based on your current cell. So if you're at column 0 you wouldn't check column -1 or if you're at row = <# of rows -1> don't check row + 1 etc.

 

Or you could add a row of padding around the entire board and not worry about it.

[SSL]

I think a loop is probably the best way to do it. Do you have any other suggestions? 

 

Padding, as suggested. Unrolling the loop wouldn't be so bad, though. Experiment, there are a number of ways to solve the problem.

[namarino]

If you want to stick with a loop you could either get the minimum and maximum row and column before looping based on your current cell. So if you're at column 0 you wouldn't check column -1 or if you're at row = <# of rows -1> don't check row + 1 etc.

 

Or you could add a row of padding around the entire board and not worry about it.

 

Padding, as suggested. Unrolling the loop wouldn't be so bad, though. Experiment, there are a number of ways to solve the problem.

Alright cool, thanks guys, I really appreciate your help!