Java Tetris-遍历双数组

Question

I'm building tetris and am trying to implement a method which iterates through grid[][] of tiles and checks each column per row, starting from the bottom, working its way up (figured it'd be a faster check if I started from the bottom since that's where most rows will need to be cleared).

My understanding of this is- create a double for loop, for each row, check if all columns in that row are full (not null). If they are, I will implement a clear (which is really setting the current row = rows above). For now, I am just trying to output "Full".

My System.out.println(grid[row][col] + ", " + row + ", " + col); check correctly shows that it's starting at the bottom row, then iterating each column... but the if (grid[row][col] != null) { check doesn't seem to be staying on that row...

public void checkBottomFull() {
int columnsFilled = 0;
    //loops through rows only after each column has finished
    for(int row = grid.length-2; row > 0; row--) {
        //loops through all columns per row, then row decrements
        for(int col = 0; col < grid[row].length; col++) {
            System.out.println(grid[row][col] + ", " + row + ", " + col);       
            if (grid[row][col] != null) {
                columnsFilled++;
                if (columnsFilled == grid.length-1) {
                    System.out.println("full");     
                }
            }
        }
    }
}

Any thoughts?

---

EDIT

public void checkBottomFull() {
    for(int row = grid.length-1; row >= 0; row--) {
        //loops through columns of each individual row
        if (isFull(row)) {
            System.out.println("full");
            clearRow(row);      
        }
    }
}

public boolean isFull(int row) {
    for (int col = 0; col < grid[row].length-1; col++) {
         if(grid[row][col] == null) {
             System.out.println(grid[row][col] + "... " + row + ", " + col);
             return false;
         }
    }   
    return true;
}

public void clearRow(int row) {
    for (int col = 0; col < grid[row].length-1; col++) {
        System.out.println("clearing...");
        grid[row][col] = grid[row-1][col];
    }
}

System.out.println(grid[row][col] + "... " + row + ", " + col); outputs: Why isn't column incrementing?

null... 9, 0
null... 8, 0
null... 7, 0
null... 6, 0
null... 5, 0
null... 4, 0
null... 3, 0
null... 2, 0
null... 1, 0
null... 0, 0

Answer 1

Few problems here:

1. You should move int columnsFilled = 0 inside the outer for loop since it's suppose to be a check of the current row only. As it is now, after you get past the first row the count will be incorrect.
2. You are checking if (columnsFilled == grid.length-1) when in fact this should be if (columnsFilled == grid[row].length-1) . Your check compares the number of filled columns against the number of rows, instead of against the number of columns in the given row.

Answer 2

You might consider adding a convenience function similar to

public boolean isFullRow(Tile[][] grid, int row)
{
    for(int i=0; i<grid[row].length; i++)
    {
        if(grid[row][i] == null){ return false; }
    }
    return true;
}

This would help debug your code, as well as make it (slightly but not noticeably) faster.

Then your checkButtomFull() function could look like

public void checkBottomFull() {
    //loops through rows only after each column has finished
    for(int row = grid.length-2; row > 0; row--) {
        if(isFullRow(grid, row)){
            // Do something if full row
        }
    }
}

Lastly, as a minor point, my guess is that

for(int row = grid.length-2; row > 0; row--)

could/should be written as

for(int row = grid.length-1; row >= 0; row--) {

Answer 3

There were a few logic errors in the code you posted, the attached code fixes them without implementing everything for you.

public class SampleClass {

static String[][] grid = new String[4][10];

/**
 * @param args
 */
public static void main(String[] args) {
    // TODO Auto-generated method stub
    loadGrid();
    checkBottomFull();
}
public static void checkBottomFull() {
    int columnsFilled = 0;
    //loops through rows only after each column has finished
    for(int row = grid.length-1; row >= 0; row--) {//needed 'greater than or equal to'
        columnsFilled=0; //need to reinitialize this before every iteration
        for(int col = 0; col <= grid[row].length-1; col++) { //needed 'less than or equal to'
           System.out.println(row + ", " + col+", "+grid[row][col]);       
            if (grid[row][col] != null) {
                columnsFilled++;
            }
        }
        System.out.println("columns that have a character" + columnsFilled);
        System.out.println("Needs to be "+grid[row].length+" to remove row");
        if (columnsFilled == grid[row].length) {
            System.out.println("full");   //this is where you should remove a row  
        }
    }
}

private static void loadGrid() {
    grid[0] = new String[] {"X","X","X","X","X","X","X","X","X","X"};
    grid[1] = new String[] {"X","X",null,"X","X","X",null,"X","X","X"};
    grid[2] = new String[] {"X","X","X",null,"X","X",null,"X","X","X"};
    grid[3] = new String[] {"X","X",null,"X","X","X",null,"X","X","X"};
}

}

Answer 4

public static void checkBottomFull() {

    //loops through rows only after each column has finished
    for(int row = grid.length-1; row >= 0; row--) {
        //loops through all columns per row, then row decrements
        int columnsFilled = 0;
        for(int col = 0; col < grid[row].length; col++) {
            System.out.println(grid[row][col] + ", " + row + ", " + col);       
            if (grid[row][col] != null && ++columnsFilled == grid[row].length) {
                System.out.println("full");     
            }
        }
    }
}