<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) {
        int n = grid.size();
        vector<vector<int>> adj(3 * n, vector<int>(3 * n, 0));
        for(int i = 0; i < grid.size(); i++) {
            for(int j = 0; j < grid[i].size(); j++) {
                if(grid[i][j] == ' ') continue;
                if(grid[i][j] == '/') {
                    int x = 3 * i;
                    int y = 3 * j + 2;
                    for(int k = 0; k < 3; k++) {
                        adj[x][y] = 1;
                        x++;
                        y--;
                    }
                } else if(grid[i][j] == '\\') {
                    int x = 3 * i;
                    int y = 3 * j;
                    for(int k = 0; k < 3; k++) {
                        adj[x][y] = 1;
                        x++;
                        y++;
                    }
                }
            }
        }
        
        int res = 0;
        vector<vector<bool>> vis(3 * n, vector<bool>(3 * n, false));
        for(int i = 0; i < 3 * n; i++) {
            for(int j = 0; j < 3 * n; j++) {
                if(!vis[i][j] && adj[i][j] == 0) {
                    res++;
                    bfs(adj, vis, i, j);
                }
            }
        }
        return res;
    }
    
    void bfs(vector<vector<int>>& adj, vector<vector<bool>>& vis, int x, int y) {
        queue<pair<int, int>> q;
        q.push({x, y});
        vis[x][y] = true;
        
        int xx[4] = {0, 0, 1, -1};
        int yy[4] = {1, -1, 0, 0};
        
        while(!q.empty()) {
            pair<int, int> temp = q.front();
            q.pop();
            
            for(int i = 0; i < 4; i++) {
                int x_new = xx[i] + temp.first;
                int y_new = yy[i] + temp.second;
                
                if(x_new >= 0 && x_new < adj.size() && y_new >= 0 && y_new < adj[0].size() && adj[x_new][y_new] == 0) {
                    if(vis[x_new][y_new]) continue;
                    vis[x_new][y_new] = true;
                    q.push({x_new, y_new});
                }
            }
        }
    }
};
20326