Method dfs

python/0695-max-area-of-island.py:6–17

(r, c)

        visit = set()

        def dfs(r, c):
            if (
                r < 0
                or r == ROWS
                or c < 0
                or c == COLS
                or grid[r][c] == 0
                or (r, c) in visit
            ):
                return 0
            visit.add((r, c))
            return 1 + dfs(r + 1, c) + dfs(r - 1, c) + dfs(r, c + 1) + dfs(r, c - 1)

        area = 0
        for r in range(ROWS):