Answer by 200_success for Find maximum area of island in matrix

Your code is somewhat Pythonic, but could use some improvements.

You seem to be under the impression that you are exploring each island by performing a breadth-first-search using a queue (named q). Actually, you are performing a depth-first-search using a stack. (You can't .pop() a queue!)

for _,d in enumerate(dirs) is a pointless use of enumerate(), and it should be written as for d in dirs.

If you name the bounds as rlen and clen, then I would prefer that you use r and c (instead of i and j) for your coordinates.

Your add_dir() function is a bit clumsy. You return (-1, -1) if the result is out of bounds, which means that the caller also has to check whether the result is out of bounds. What you want is a neighbors(r, c) function that lists all of the neighbor coordinates of (r, c) that are in bounds. One Pythonic technique that you can use is to write it as a generator. Another trick is to use chained comparisons (e.g. x < y <= z).

It's a bit uncouth to initialize the elements of visited to 0, then set some of them to True, mixing integers with booleans.

A more readable way to express the goal of the max_area_of_island() function would be:

return max(island_size(r, c) for r, c in product(range(rlen), range(clen)))

… taking advantage of itertools.product() to avoid a nested loop. I have therefore reorganized the code to provide an island_size() function to enable that.

from itertools import productdef max_area_of_island(grid):    rlen, clen = len(grid), len(grid[0])    def neighbors(r, c):"""        Generate the neighbor coordinates of the given row and column that        are within the bounds of the grid."""        for dr, dc in [(-1, 0), (1, 0), (0, -1), (0, 1)]:            if (0 <= r + dr < rlen) and (0 <= c + dc < clen):                yield r + dr, c + dc    visited = [[False] * clen for _ in range(rlen)]    def island_size(r, c):"""        Find the area of the land connected to the given coordinate.        Return 0 if the coordinate is water or if it has already been        explored in a previous call to island_size()."""        if grid[r][c] == 0 or visited[r][c]:            return 0        area = 1        stack = [(r, c)]        visited[r][c] = True        while stack:            for r, c in neighbors(*stack.pop()):                if grid[r][c] and not visited[r][c]:                    stack.append((r, c))                    visited[r][c] = True                    area += 1        return area    return max(island_size(r, c) for r, c in product(range(rlen), range(clen)))