<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) {
        const int n = grid[0].size() * 3;
        vector<vector<int>> g = vector(n, vector<int>());

        for(int i=0; i<grid.size(); ++i){
            const int row = i*3;
            for(int j=0; j<grid[i].size(); ++j){
                const char c = grid[i][j];
                if(c == ' '){
                    append(g[row], {0,0,0});
                    append(g[row+1], {0,0,0});
                    append(g[row+2], {0,0,0});
                } 
                else if(c == '/'){
                    append(g[row], {0,0,1});
                    append(g[row+1], {0,1,0});
                    append(g[row+2], {1,0,0});
                } 
                else{
                    append(g[row], {1,0,0});
                    append(g[row+1], {0,1,0});
                    append(g[row+2], {0,0,1});
                }
            }
        }

        int ans = 0;

        for(int i=0; i<g.size(); ++i){
            for(int j=0; j<g[i].size(); ++j){
                if(g[i][j] == 0){
                    mark(g, i, j);
                    ++ans;
                } 
            }
        }

        return ans;
    }

    void mark(vector<vector<int>>& g, int x, int y){
        if(x < 0 || x >= g.size() || y < 0 || y >= g[x].size() || g[x][y] == 1) return;

        g[x][y] = 1;

        const int d[3] = {-1, 0, 1};

        for(auto dx: d){
            for(auto dy: d){
                if(abs(dx) == abs(dy)) continue;
                mark(g, x+dx, y+dy);
            }
        }
    }

    void append(vector<int>& v, vector<int> ap){
        for(auto i: ap){
            v.push_back(i);
        }
    }

    void print(vector<int>& v){
        for(auto i: v){
            cout << i << " ";
        }
        cout << "\n";
    }

    void print(vector<vector<int>>& v){
        for(auto i: v){
            print(i);
        }
    }
};
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