<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 {
public:
    int regionsBySlashes(vector<string>& grid) {
        int h = grid.size();
        int w = grid[0].size();

        vector<vector<int>> ex_grid(3 * h, vector<int>(3 * w, 0));

        for (int i = 0; i < h; ++i) {
            for (int j = 0; j < w; ++j) {
                if (grid[i][j] == '/') {
                    ex_grid[i * 3][j * 3 + 2] = 1;
                    ex_grid[i * 3 + 1][j * 3 + 1] = 1;
                    ex_grid[i * 3 + 2][j * 3] = 1;
                } else if (grid[i][j] == '\\') {
                    ex_grid[i * 3][j * 3] = 1;
                    ex_grid[i * 3 + 1][j * 3 + 1] = 1;
                    ex_grid[i * 3 + 2][j * 3 + 2] = 1;
                }
            }
        }

        int regions = 0;
        for (int i = 0; i < 3 * h; ++i) {
            for (int j = 0; j < 3 * w; ++j) {
                if (ex_grid[i][j] == 0) {
                    bfs(ex_grid, i, j, 3 * h, 3 * w);
                    ++regions;
                }
            }
        }

        return regions;
    }

private:
    void bfs(vector<vector<int>>& ex_grid, int x, int y, int h, int w) {
        queue<pair<int, int>> q;
        q.push({x, y});
        ex_grid[x][y] = 1;

        vector<int> dirX = {-1, 1, 0, 0};
        vector<int> dirY = {0, 0, -1, 1};

        while (!q.empty()) {
            auto [cx, cy] = q.front();
            q.pop();

            for (int i = 0; i < 4; ++i) {
                int nx = cx + dirX[i];
                int ny = cy + dirY[i];

                if (nx >= 0 && nx < h && ny >= 0 && ny < w && ex_grid[nx][ny] == 0) {
                    ex_grid[nx][ny] = 1;
                    q.push({nx, ny});
                }
            }
        }
    }
};

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