<p>An <code>n x n</code> grid is composed of <code>1 x 1</code> squares where each <code>1 x 1</code> square consists of a <code>&#39;/&#39;</code>, <code>&#39;\&#39;</code>, or blank space <code>&#39; &#39;</code>. These characters divide the square into contiguous regions.</p>

<p>Given the grid <code>grid</code> represented as a string array, return <em>the number of regions</em>.</p>

<p>Note that backslash characters are escaped, so a <code>&#39;\&#39;</code> is represented as <code>&#39;\\&#39;</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2018/12/15/1.png" style="width: 200px; height: 200px;" />
<pre>
<strong>Input:</strong> grid = [&quot; /&quot;,&quot;/ &quot;]
<strong>Output:</strong> 2
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2018/12/15/2.png" style="width: 200px; height: 198px;" />
<pre>
<strong>Input:</strong> grid = [&quot; /&quot;,&quot;  &quot;]
<strong>Output:</strong> 1
</pre>

<p><strong class="example">Example 3:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2018/12/15/4.png" style="width: 200px; height: 200px;" />
<pre>
<strong>Input:</strong> grid = [&quot;/\\&quot;,&quot;\\/&quot;]
<strong>Output:</strong> 5
<strong>Explanation: </strong>Recall that because \ characters are escaped, &quot;\\/&quot; refers to \/, and &quot;/\\&quot; refers to /\.
</pre>

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

<ul>
	<li><code>n == grid.length == grid[i].length</code></li>
	<li><code>1 &lt;= n &lt;= 30</code></li>
	<li><code>grid[i][j]</code> is either <code>&#39;/&#39;</code>, <code>&#39;\&#39;</code>, or <code>&#39; &#39;</code>.</li>
</ul>

class Solution:
    # right left down up
    directions = [(0,1),(0, -1),(1,0),(-1,0)]
    def regionsBySlashes(self, grid: List[str]) -> int:

        grid_size = len(grid)

        # turn each cell in grid into a 3 x 3 grid
        expandedGrid = [[0] * (grid_size * 3) for _ in range(grid_size * 3)]

        # convert each cell into a 3x3 grid
        for i in range(grid_size):
            for j in range(grid_size):
                base_row = i * 3
                base_col = j * 3
                if grid[i][j] == "\\":
                    expandedGrid[base_row][base_col] = 1
                    expandedGrid[base_row+1][base_col+1] = 1
                    expandedGrid[base_row+2][base_col+2] = 1
                elif grid[i][j] == "/":
                    expandedGrid[base_row][base_col+2] = 1
                    expandedGrid[base_row+1][base_col+1] = 1
                    expandedGrid[base_row+2][base_col] = 1

        region_count = 0
        # run driver over each cell:
        # if unvisited cell, flood fill it and its region and inc region count by 1

        for r in range(grid_size*3):
            for c in range(grid_size*3):

                if expandedGrid[r][c] == 0:
                    self.floodFill(expandedGrid, r, c)
                    region_count += 1

        return region_count

    def floodFill(self, expandedGrid, r, c):
        Q = collections.deque([(r, c)])
        expandedGrid[r][c] = 1

        while Q:
            r, c = Q.popleft()

            for dr, dc in self.directions:
                rdr, cdc =r+dr, c + dc
                if self.isValidCell(expandedGrid,rdr, cdc):
                    expandedGrid[rdr][cdc] = 1
                    Q.append((rdr, cdc))

    def isValidCell(self, expandedGrid, r ,c):
        '''
            check if in bounds and unvisited
        '''
        n = len(expandedGrid)
        return ((0 <= r < n) and (0 <= c < n) and expandedGrid[r][c] == 0)


        
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