<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 {
    vector<vector<int>> directions = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
    void dfs(vector<vector<int>>& matrix, int r, int c)
    {
        int L = matrix.size();
        matrix[r][c] = -1;
        for(auto& dir : directions)
        {
            int new_r = r + dir[0];
            int new_c = c + dir[1];
            if(new_r >= 0 && new_r < L && new_c >= 0 && new_c < L 
            && matrix[new_r][new_c] != -1)
            {
                dfs(matrix, new_r, new_c);
            }
        }
    }

public:
    int regionsBySlashes(vector<string>& grid) {
        int L = grid.size();

        vector<vector<int>> matrix(L * 3, vector<int>(L * 3, 0));

        int r = 0, c = 0;

        for(int i = 0; i < L; i++)
        {
            c = 0;
            auto s = grid[i];
            for(int k = 0; k < s.length(); k++)
            {
                if(s[k] == '/')
                {
                    matrix[r][c + 2] = -1;
                    matrix[r + 1][c + 1] = -1;
                    matrix[r + 2][c] = -1;
                }
                else if (s[k] == '\\')
                {
                    matrix[r][c] = -1;
                    matrix[r + 1][c + 1] = -1;
                    matrix[r + 2][c + 2] = -1;
                }
                c += 3;
            }

            r += 3;
        }

        int islands = 0;
        for(int r = 0; r < 3* L; r++)
        {
            for(int c = 0; c < 3* L; c++)
            {
                if(matrix[r][c] != -1)
                {
                    islands++;
                    dfs(matrix, r, c);
                }
            }
        }

        return islands;
    }
};
14073