使用洪水填充算法计算 0 的数量

Question

I wanted to count number of 0 and 1 from a 2d array with floodfill algorithm....But unfortunetly...it's showing the wrong result.

I have a matrix like this

0,1,1,0,1

1,0,1,1,0

1,0,1,1,0

1,0,1,1,0

1,0,1,1,0

It supposed to show number of 0 = 10 and 1 =15

but it showing number of 0 = 4 and 1 = 21

here is my code

int[][] input;
public static int[,] reult;
public static int count = 0,col,row;
public Form1()
{
    InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
    string path;
    OpenFileDialog file = new OpenFileDialog();
    if (file.ShowDialog() == DialogResult.OK)
    {

        input = File.ReadLines(file.FileName)
                .Skip(0)
                .Select(l => l.Split(',')
                    .Select(n => int.Parse(n))
                    .ToArray())
                    .ToArray();

    }

    reult = JaggedToMultidimensional(input);

    int p = reult.GetLength(0); 
    int q = reult.GetLength(1); 
    row = p-1;
    col = q - 1;
    int one = p * q;
    int zero = apply(row, col);
    label1.Text = "" + zero;
    label2.Text = "" + (one - zero);

}

public T[,] JaggedToMultidimensional<T>(T[][] jaggedArray)
{
    int rows = jaggedArray.Length;
    int cols = jaggedArray.Max(subArray => subArray.Length);
    T[,] array = new T[rows, cols];
    for (int i = 0; i < rows; i++)
    {
        for (int j = 0; j < cols; j++)
        {
            array[i, j] = jaggedArray[i][j];
        }
    }
    return array;
}

private static int apply(int x, int y)
{
    int currentColor = getValueAt(x, y);
    if (currentColor == 0)
    {
        visit(x, y);
        count++;

        if (x < row) apply(x + 1, y);
        if(y<col) apply(x, y + 1);
       if(x>0) apply(x - 1, y);
       if (y>0) apply(x, y - 1);
    }
    return count;
}

private static int getValueAt(int x, int y)
{
    if (x < 0 || y < 0 || x > row || y > col)
    {
        return -1;
    }
    else
    {
        return reult[x,y];
    }
}

private static void visit(int x, int y)
{
    reult[x,y] = 1;
}

Answer 1

int zero = apply(row, col);

In your flood fill algorithm, you are only going in four direction and cover the area which match your criteria. And fortunately [row,col] index has 0 and it count all four 0 from [row, col] . Now think what if apply(row,col) have 1 on that row, col index.

To get this thing right, you need to loop through whole matrix and call apply(i,j) where ever you find an array[i,j]==0

Change this line

int zero = apply(row, col);

to

int zero = 0;
for(int i=0; i<=row; i++)
{
   for(int j=0; j<=col; j++)
   {
       if(array[i][j]==0)
       {
          count =0;
          zero+= apply(row, col);
       }
   }
}

Hope this helps.

Answer 2

Given the requirements you should change the search criteria to search for 0's and 1's.

What you need to do is to search within the rectangle so the border of the rectangle is limit for searching.

ie

int[] count = {0,0};

private static int apply(int x, int y)
{
    int currentColor = getValueAt(x, y);
    if (currentColor != -1)
    {
        visit(x, y);
        count[currentColor]++;

        if (x < row) apply(x + 1, y);
        if(y<col) apply(x, y + 1);
       if(x>0) apply(x - 1, y);
       if (y>0) apply(x, y - 1);
    }
    return count;
}

and then change your visit function to set the cell to -1 instead to avoid visiting it twice.

Answer 3

You can also use linq if you want (I actually prefer):

OpenFileDialog fileDialog = new OpenFileDialog();
            if (fileDialog.ShowDialog() == DialogResult.OK)
            {
                var lines = File.ReadLines(fileDialog.FileName);
                var splittedValues = lines.Where(l => !string.IsNullOrEmpty(l)).Select(l => l.Split(',')).SelectMany(l => l).ToList();
                var valCount = splittedValues.GroupBy(s => s).Select(s => new { val = s.Key, count = s.Count() }).ToList();     
            }

It will give you following result:

[0] { val= "0", count=10} [1] { val= "1", count=15}