<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:
        ans = 0
        for island in getIslands(grid2):
            is_sub = True
            for (i,j) in island:
                if grid1[i][j] == 0:
                    is_sub = False
                    break
            ans += is_sub
        return ans

def getIslands(grid):
    points = {(i,j) for i in range(len(grid)) for j in range(len(grid[0]))}
    islands = []
    while len(points):
        point = points.pop()
        i,j = point
        if grid[i][j] == 0:
            try:
                points.remove((i,j))
            except KeyError:
                pass
        else:
            #foreach adjacent point add to island and pop from set so not re-traversed
            #then do the same for adjacent points
            island = [point]
            seen_adjacent_points = set(island)
            adjacent_stack = [(i+1,j), (i-1,j), (i,j+1), (i,j-1)]
            while len(adjacent_stack):
                point2 = adjacent_stack.pop()
                i2,j2 = point2
                if i2<0 or i2 >= len(grid) or j2<0 or j2 >= len(grid[0]):
                    continue
                try:
                    points.remove(point2)
                except KeyError:
                    pass
                if point2 in seen_adjacent_points:
                    continue
                try:
                    points.remove(point2)
                except KeyError:
                    pass
                seen_adjacent_points.add(point2)
                if grid[i2][j2] == 1:
                    adjacent_stack += [(i2+1,j2), (i2-1,j2), (i2,j2+1), (i2,j2-1)]
                    island.append(point2)
            islands.append(island)
    #print(islands)
    return islands
53790