Number of islands

gistfile1.txt

class Solution:
    def numIslands(self, grid: List[List[str]]) -> int:
        
        num_island = 0
        queue = deque()
        for x in range(len(grid)):
            for y in range(len(grid[0])):
                if grid[x][y] == "1":
                    queue.append((x, y))
                    while queue:
                        i, j = queue.popleft()
                        grid[i][j] = None # mark this cell as visited
                        for (i2, j2) in [(i - 1, j), (i + 1, j), 
                                         (i, j - 1), (i, j + 1)]:
                            if 0 <= i2 < len(grid) and 0 <= j2 < len(grid[0]) and grid[i2][j2] == "1":
                                queue.append((i2, j2))
                    num_island += 1
                    
        return num_island