<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:
    void bfs(int x, int y, vector<vector<bool>>& vis, vector<vector<int>>& g, int size) {
        queue<pair<int, int>> q;
        q.push({x, y});
        vis[x][y] = true;
        int dx[] = {1, -1, 0, 0};
        int dy[] = {0, 0, 1, -1};
        while (!q.empty()) {
            auto [cx, cy] = q.front();
            q.pop();
            for (int k = 0; k < 4; k++) {
                int nx = cx + dx[k];
                int ny = cy + dy[k];
                if (nx >= 0 && ny >= 0 && nx < size && ny < size && !vis[nx][ny] && g[nx][ny] == 0) {
                    vis[nx][ny] = true;
                    q.push({nx, ny});
                }
            }
        }
    }
    int regionsBySlashes(vector<string>& grid) {
        int n = grid.size();
        vector<vector<int>> g(n * 3, vector<int>(n * 3, 0));
        vector<vector<bool>> vis(n * 3, vector<bool>(n * 3, false));
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                if (grid[i][j] == '/') {
                    g[i * 3][j * 3 + 2] = g[i * 3 + 1][j * 3 + 1] = g[i * 3 + 2][j * 3] = 1;
                } else if (grid[i][j] == '\\') {
                    g[i * 3][j * 3] = g[i * 3 + 1][j * 3 + 1] = g[i * 3 + 2][j * 3 + 2] = 1;
                }
            }
        }
        int regions = 0;
        for (int i = 0; i < n * 3; i++) {
            for (int j = 0; j < n * 3; j++) {
                if (!vis[i][j] && g[i][j] == 0) {
                    regions++;
                    bfs(i, j, vis, g, n * 3);
                }
            }
        }
        return regions;
    }
};
20478