Smallest Rectangle Enclosing Black Pixels (diff)

1. This very nice. Different from traditional DFS, you don't have to find every possible route. You just need to cover every black pixel.

public class Solution {
    private void dfs(char[][] image, int x, int y, ArrayList<Integer> coordinate){
        if(x<0 || x>=image.length || y<0 || y>= image[0].length || image[x][y] !='1' ){
            return;
        }
        coordinate.set(0, Math.min(coordinate.get(0), x));
        coordinate.set(1, Math.min(coordinate.get(1), y));
        coordinate.set(2, Math.max(coordinate.get(2), x));
        coordinate.set(3, Math.max(coordinate.get(3), y));
        image[x][y] = '2';
        dfs(image, x-1, y, coordinate);
        dfs(image, x+1, y, coordinate);
        dfs(image, x, y-1, coordinate);
        dfs(image, x, y+1, coordinate);
    }
    public int minArea(char[][] image, int x, int y) {
        ArrayList<Integer> coordinate = new ArrayList<>();
        //0 -> x1, as small as possible,  1 -> y1 as small as possible
        //2 -> x2, as large as possible,  3 -> y2 as large as possible
        coordinate.add(Integer.MAX_VALUE);
        coordinate.add(Integer.MAX_VALUE);
        coordinate.add(Integer.MIN_VALUE);
        coordinate.add(Integer.MIN_VALUE);
        dfs(image, x, y, coordinate);
        return (coordinate.get(2)-coordinate.get(0)+1) * (coordinate.get(3) - coordinate.get(1)+1);
    }
}