这张网格有几个岛

四行四列，1 是陆地 0 是海。上下左右相邻算同一个岛。运行下面这段程序，看岛数 / 最大的岛多大 / 陆地总格数：

def islands(g, dirs):
    m = len(g)
    n = len(g[0])
    seen = set()
    cnt = 0
    sizes = []
    for i in range(m):
        for j in range(n):
            if g[i][j] != 1 or (i, j) in seen:
                continue
            cnt += 1
            st = [(i, j)]
            seen.add((i, j))
            sz = 0
            while st:
                x, y = st.pop()
                sz += 1
                for dx, dy in dirs:
                    a, b = x + dx, y + dy
                    if (0 <= a < m and 0 <= b < n
                            and g[a][b] == 1 and (a, b) not in seen):
                        seen.add((a, b))
                        st.append((a, b))
            sizes.append(sz)
    return cnt, sizes

D4 = ((1, 0), (-1, 0), (0, 1), (0, -1))
D8 = D4 + ((1, 1), (1, -1), (-1, 1), (-1, -1))

g = [[1, 1, 0, 0], [1, 0, 0, 1], [0, 0, 1, 0], [1, 0, 0, 0]]
c, sz = islands(g, D4)
print(str(c) + "/" + str(max(sz)) + "/" + str(sum(sz)))