<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() << 2, m = grid[0].size() << 2;
        vector<vector<int>> t(n, vector<int>(m, 0));
        for (int i = 0; i < grid.size(); ++i) {
            for (int j = 0; j < grid[i].size(); ++j) {
                switch (grid[i][j]) {
                case '/':
                    t[(i << 2) + 0][(j << 2) + 3] = 1;
                    t[(i << 2) + 1][(j << 2) + 2] = 1;
                    t[(i << 2) + 2][(j << 2) + 1] = 1;
                    t[(i << 2) + 3][(j << 2) + 0] = 1;
                    break;
                case '\\':
                    t[(i << 2) + 0][(j << 2) + 0] = 1;
                    t[(i << 2) + 1][(j << 2) + 1] = 1;
                    t[(i << 2) + 2][(j << 2) + 2] = 1;
                    t[(i << 2) + 3][(j << 2) + 3] = 1;
                    break;

                }
            }
        }

        vector<vector<int>> direct = { {0, 1}, {0, -1}, {1, 0}, {-1, 0} };
        auto isNotVisit = [&t](int x, int y) -> bool {
            return x >= 0 && x < t.size() && y >= 0 && y < t[0].size() && t[x][y] == 0;
            };

        queue<pair<int, int>> q;
        int res = 0;
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < m; ++j) {
                if (t[i][j] > 0) continue;

                q.push({ i, j });
                while (!q.empty()) {
                    auto item = q.front();
                    q.pop();
                    if (t[item.first][item.second] > 0) continue;
                    t[item.first][item.second] = 1;
                    for (auto& d : direct) {
                        int x = item.first + d[0], y = item.second + d[1];
                        if (isNotVisit(x, y)) {
                            q.push({ x, y });
                        }
                    }
                }
                ++res;
            }
        }

        return res;
    }
};
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