<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 dfs(vector<vector<int>> &vec, int i, int j){
        if (min(i,j) < 0 || i >= vec.size() || j >= vec.size() || vec[i][j] == 1){
            return;
        }

        vec[i][j] = 1;
        dfs(vec, i + 1, j);
        dfs(vec, i, j + 1);
        dfs(vec, i - 1, j);
        dfs(vec, i, j - 1);
    }

    int regionsBySlashes(vector<string>& grid) {

        int n = grid.size();
        if (!n) return 0;

        vector<vector<int>> vec(n * 3, vector<int> (n * 3));
        for (int i = 0; i < n; ++i){
            for(int j = 0; j < n; ++j){
                if (grid[i][j] == '/')
                    vec[(i * 3)][(j * 3)+2] = vec[(i * 3)+1][(j * 3)+1] = vec[(i * 3)+2][(j * 3)] = 1;
                else if (grid[i][j] == '\\')
                    vec[i * 3][j * 3] = vec[i * 3 + 1][j * 3 + 1] = vec[i * 3 + 2][j * 3 + 2] = 1;
            }
        }

        int regions = 0;
        for (int i = 0; i < vec.size(); ++i){
            for (int j = 0; j < vec[i].size(); ++j){
                if (!vec[i][j]){
                    dfs(vec, i, j);
                    ++regions;
                }
            }
        }

        return regions;

    }
};
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