<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 fillBox(vector<vector<int>>& matrix, char ch, int i, int j) {
        if (ch == ' ') return;
        else if (ch == '/') {
            matrix[i][j + 3] = 1;
            matrix[i + 1][j + 2] = 1;
            matrix[i + 2][j + 1] = 1;
            matrix[i + 3][j] = 1;
        }
        else {
            matrix[i][j] = 1;
            matrix[i + 1][j + 1] = 1;
            matrix[i + 2][j + 2] = 1;
            matrix[i + 3][j + 3] = 1;
        }
    }

    void bfsFill(vector<vector<int>>& matrix, int i, int j) {
        int sizeI = matrix.size(), sizeJ = matrix[0].size();
        queue<pair<int, int>> q;
        q.push({ i,j });
        matrix[i][j] = 1;

        int arrI[] = { 0,1 };
        int arrj[] = { 1,0 };

        while (!q.empty()) {
            int indexI = q.front().first, indexJ = q.front().second;
            q.pop();

            if (indexJ + 1 < sizeJ && matrix[indexI][indexJ + 1] == 0) {
                matrix[indexI][indexJ + 1] = 1;
                q.push({ indexI, indexJ + 1 });
            }
            if (indexJ - 1 >= 0 && matrix[indexI][indexJ - 1] == 0) {
                matrix[indexI][indexJ - 1] = 1;
                q.push({ indexI, indexJ - 1 });
            }
            if (indexI + 1 < sizeI && matrix[indexI + 1][indexJ] == 0) {
                matrix[indexI + 1][indexJ] = 1;
                q.push({ indexI + 1, indexJ });
            }
            if (indexI - 1 >= 0 && matrix[indexI - 1][indexJ] == 0) {
                matrix[indexI - 1][indexJ] = 1;
                q.push({ indexI - 1, indexJ });
            }
        }
    }

    int regionsBySlashes(vector<string>& grid) {
        int rows = 4 * grid.size(), col = 4 * grid[0].size();
        vector<vector<int>> matrix(rows, vector<int>(col));
        int i = 0, j = 0, ans = 0;
        for (string st : grid) {
            j = 0;
            for (char ch : st) {
                if (ch != ' ') {
                    fillBox(matrix, ch, i, j);
                }
                j = j + 4;
            }
            i = i + 4;
        }

        for (int i = 0; i < matrix.size(); i++) {
            for (int j = 0; j < matrix[0].size(); j++) {
                if (matrix[i][j] == 0) {
                    bfsFill(matrix, i, j);
                    ++ans;
                }
            }
        }
        return ans;
    }
};
23071