public class AshCloud {
 
    public AshCloud (int n, double f) {
        double[][] grid = new double[n][n];
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                grid[i][j] = 0.0;
            }
        }
        grid[n/2][n/2] = 1.0;
    }
    public double [][] runSimulation (char dir , int steps ) {
        double[][] grid = new double[n][n];
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                grid[i][j] = 0.0;
            }
        }
        grid[n/2][n/2] = 1.0;
        
        if (dir == "N") {
            for (int i = 0; i < steps; i++) {
                for (int j = 0; j < n; j++) {
                    grid[i][j] = grid[i][j] * (1-f) + grid[i+1][j] * f;
                }
            }
        }
        if (dir == "S") {
            for (int i = 0; i < steps; i++) {
                for (int j = 0; j < n; j++) {
                    grid[i][j] = grid[i][j] * (1-f) + grid[i-1][j] * f;
                }
            }
        }
        if (dir == "E") {
            for (int i = 0; i < steps; i++) {
                for (int j = 0; j < n; j++) {
                    grid[i][j] = grid[i][j] * (1-f) + grid[i][j+1] * f;
                }
            }
        }
        if (dir == "W") {
            for (int i = 0; i < steps; i++) {
                for (int j = 0; j < n; j++) {
                    grid[i][j] = grid[i][j] * (1-f) + grid[i][j-1] * f;
                }
            }
        }
    }
}