1905-Count-Sub-Islands.py

class Solution:
    def countSubIslands(self, grid1: List[List[int]], grid2: List[List[int]]) -> int:
        ROWS, COLS = len(grid1), len(grid1[0])
        visit = set()

        def dfs(r, c):
            if (
                r < 0
                or c < 0
                or r == ROWS
                or c == COLS
                or grid2[r][c] == 0
                or (r, c) in visit
            ):
                return True

            visit.add((r, c))
            res = True
            if grid1[r][c] == 0:
                res = False

            res = dfs(r - 1, c) and res
            res = dfs(r + 1, c) and res
            res = dfs(r, c - 1) and res
            res = dfs(r, c + 1) and res
            return res

        count = 0
        for r in range(ROWS):
            for c in range(COLS):
                if grid2[r][c] and (r, c) not in visit and dfs(r, c):
                    count += 1
        return count