<p>You are given two <code>m x n</code> binary matrices <code>grid1</code> and <code>grid2</code> containing only <code>0</code>&#39;s (representing water) and <code>1</code>&#39;s (representing land). An <strong>island</strong> is a group of <code>1</code>&#39;s connected <strong>4-directionally</strong> (horizontal or vertical). Any cells outside of the grid are considered water cells.</p>

<p>An island in <code>grid2</code> is considered a <strong>sub-island </strong>if there is an island in <code>grid1</code> that contains <strong>all</strong> the cells that make up <strong>this</strong> island in <code>grid2</code>.</p>

<p>Return the <em><strong>number</strong> of islands in </em><code>grid2</code> <em>that are considered <strong>sub-islands</strong></em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/06/10/test1.png" style="width: 493px; height: 205px;" />
<pre>
<strong>Input:</strong> grid1 = [[1,1,1,0,0],[0,1,1,1,1],[0,0,0,0,0],[1,0,0,0,0],[1,1,0,1,1]], grid2 = [[1,1,1,0,0],[0,0,1,1,1],[0,1,0,0,0],[1,0,1,1,0],[0,1,0,1,0]]
<strong>Output:</strong> 3
<strong>Explanation: </strong>In the picture above, the grid on the left is grid1 and the grid on the right is grid2.
The 1s colored red in grid2 are those considered to be part of a sub-island. There are three sub-islands.
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/06/03/testcasex2.png" style="width: 491px; height: 201px;" />
<pre>
<strong>Input:</strong> grid1 = [[1,0,1,0,1],[1,1,1,1,1],[0,0,0,0,0],[1,1,1,1,1],[1,0,1,0,1]], grid2 = [[0,0,0,0,0],[1,1,1,1,1],[0,1,0,1,0],[0,1,0,1,0],[1,0,0,0,1]]
<strong>Output:</strong> 2 
<strong>Explanation: </strong>In the picture above, the grid on the left is grid1 and the grid on the right is grid2.
The 1s colored red in grid2 are those considered to be part of a sub-island. There are two sub-islands.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>m == grid1.length == grid2.length</code></li>
	<li><code>n == grid1[i].length == grid2[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 500</code></li>
	<li><code>grid1[i][j]</code> and <code>grid2[i][j]</code> are either <code>0</code> or <code>1</code>.</li>
</ul>

class Solution:
    def countSubIslands(self, grid1: List[List[int]], grid2: List[List[int]]) -> int:
        # I think break into two steps

        def add_adjacent(row, column, to_visit):
            for r, c in [(1, 0), (-1, 0), (0, 1), (0, -1)]:
                if (row + r, column + c) in land2:
                    to_visit.append((row + r, column + c))
            return to_visit

        # Step 1: identify islands in 2
        land1 = set()
        land2 = set()

        # Note, could only be a subisland if in both, is good to also do grid 1
        for x in range(len(grid2)):
            for y in range(len(grid2[0])):
                if grid2[x][y] == 1:
                    land2.add((x, y))

        # Now we have where all pieces of land are
        visited = set()

        islands = []

        while land2:
            current_land = land2.pop()
            if current_land in visited:
                continue
            current_island = [current_land]
            visited.add(current_land)
            to_visit = deque()
            add_adjacent(current_land[0], current_land[1], to_visit)
            while to_visit:
                next_land = to_visit.pop()
                if next_land in visited:
                    continue
                visited.add(next_land)
                current_island.append(next_land)
                add_adjacent(next_land[0], next_land[1], to_visit)
            islands.append(current_island)
        
        # Now we have all the islands in 2
        num_sub = 0

        for island in islands:
            for r, c in island:
                if grid1[r][c] != 1:
                    break
            else:
                num_sub += 1
        return num_sub

        # Step 2: check if subisland
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