README.md

Usage

cat fixtures | python3 floodfill.py

fixture

4
4
1100
0110
0010
1000

floodfill.py

# Input
# 4
# 4
# 1100
# 0110
# 0010
# 1000

class GridAnalyser(object):
    def __init__(self):
        self.tmp_count, self.max_count = 0, 0

    def analyse_grid(self, grid):
        for y in range(grid.height):
            for x in range(grid.width):
                self.tmp_count = 0
                grid.fill(x, y, self)
                self.max_count = max(self.max_count, self.tmp_count)


class Grid(object):
    def __init__(self, width, height):
        self.width, self.height = width, height
        self.grid = []
        for y in range(self.height):
            line = []
            for x in range(self.width):
                line.append(0)
            self.grid.append(line)

    def set(self, x, y, val):
        self.grid[y][x] = val

    def fill(self, x, y, analyser):
        if x < 0 or y < 0 or x >= self.width or y >= self.height:
            return

        # out of the zone to fill
        if self.grid[y][x] != 1:
            return

        self.grid[y][x] = 2
        analyser.tmp_count += 1

        self.fill(x - 1, y, analyser)
        self.fill(x + 1, y, analyser)
        self.fill(x, y - 1, analyser)
        self.fill(x, y + 1, analyser)

        # Diagonals
        self.fill(x - 1, y - 1, analyser)
        self.fill(x + 1, y - 1, analyser)
        self.fill(x - 1, y + 1, analyser)
        self.fill(x + 1, y + 1, analyser)


def main():
    height, width = int(input()), int(input())
    grid = Grid(width, height)
    for y in range(height):
        line = input().strip()
        for x in range(width):
            grid.set(x, y, int(line[x]))

    analyser = GridAnalyser()
    analyser.analyse_grid(grid)
    print(analyser.max_count)


if __name__ == '__main__':
    main()