<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 dr[4]={0,0,1,-1},dc[4]={1,-1,0,0};
    void dfs(int r,int c,int n,vector<vector<int>> &mat){
        mat[r][c]=1;
        for(int k=0;k<4;k++){
            int nr = r + dr[k],nc = c + dc[k];
            if(nr>=0 && nr<n && nc>=0 && nc<n && mat[nr][nc]==0)
                dfs(nr,nc,n,mat);
        }
    }
    int regionsBySlashes(vector<string>& grid) {
        int n = grid.size();
        vector<vector<int>> mat(n*3,vector<int>(n*3,0));
        for(int i=0;i<n;i++){
            for(int j=0;j<n;j++){
                int r = i*3,c=j*3;
                if(grid[i][j]!=' ' && grid[i][j]=='\\'){
                    mat[r][c]=1;
                    mat[r+1][c+1]=1;
                    mat[r+2][c+2]=1;
                }
                else if(grid[i][j]!=' ' && grid[i][j]=='/'){
                    mat[r][c+2]=1;
                    mat[r+1][c+1]=1;
                    mat[r+2][c]=1;
                }
            }
        }
        int ans=0;
        for(int i=0;i<n*3;i++){
            for(int j=0;j<n*3;j++){
                if(mat[i][j]==0){
                    dfs(i,j,(n*3),mat);
                    ans+=1;
                }
            }
        }
        return ans;
    }
};
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