<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 &i, int &j, queue<pair<int,int>> &q, vector<vector<bool>> &g, int &n) {
        g[i][j] = 1;
        q.push({i,j});
        while(!q.empty()) {
            auto pr = q.front();
            q.pop();
            int r = pr.first , c = pr.second;
            if(r>0) {
                if(!g[r-1][c]) {
                    g[r-1][c] = 1;
                    q.push({r-1,c});
                }
            }
            if(c>0) {
                if(!g[r][c-1]) {
                    g[r][c-1] = 1;
                    q.push({r,c-1});
                }
            }
            if(r+1<=3*n) {
                if(!g[r+1][c]) {
                    g[r+1][c] = 1;
                    q.push({r+1,c});
                }
            }
            if(c+1<=3*n) {
                if(!g[r][c+1]) {
                    g[r][c+1] = 1;
                    q.push({r,c+1});
                }
            }
        }
    }
public:
    int regionsBySlashes(vector<string>& grid) {
        int n = grid.size();
        vector<vector<bool>> g(3*n+1,vector<bool>(3*n+1,0));
        for(int j = 0 ; j<3*n ; j++) {
            g[0][j] = 1;
            g[j][0] = 1;
            g[3*n][j] = 1;
            g[j][3*n] = 1;
        }
        for(int i = 0 ; i<n ; i++) {
            for(int j = 0 ; j<n ; j++) {
                if(grid[i][j]=='/') {
                    g[3*i][3*j+3] = 1;
                    g[3*i+1][3*j+2] = 1;
                    g[3*i+2][3*j+1] = 1;
                    g[3*i+3][3*j] = 1;
                }
                else if(grid[i][j]=='\\') {
                    g[3*i][3*j] = 1;
                    g[3*i+1][3*j+1] = 1;
                    g[3*i+2][3*j+2] = 1;
                    g[3*i+3][3*j+3] = 1;
                }
            }
        }
        int ans = 0;
        queue<pair<int,int>> q;
        for(int i = 0 ; i<3*n ; i++) {
            for(int j = 0 ; j<3*n ; j++) {
                if(!g[i][j]) {
                    ans++;
                    bfs(i,j,q,g,n);
                }
            }
        }
        return ans;
    }
};
16513