<p>You are given a 2D array of axis-aligned <code>rectangles</code>. Each <code>rectangle[i] = [x<sub>i1</sub>, y<sub>i1</sub>, x<sub>i2</sub>, y<sub>i2</sub>]</code> denotes the <code>i<sup>th</sup></code> rectangle where <code>(x<sub>i1</sub>, y<sub>i1</sub>)</code> are the coordinates of the <strong>bottom-left corner</strong>, and <code>(x<sub>i2</sub>, y<sub>i2</sub>)</code> are the coordinates of the <strong>top-right corner</strong>.</p>

<p>Calculate the <strong>total area</strong> covered by all <code>rectangles</code> in the plane. Any area covered by two or more rectangles should only be counted <strong>once</strong>.</p>

<p>Return <em>the <strong>total area</strong></em>. Since the answer may be too large, return it <strong>modulo</strong> <code>10<sup>9</sup> + 7</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://s3-lc-upload.s3.amazonaws.com/uploads/2018/06/06/rectangle_area_ii_pic.png" style="width: 600px; height: 450px;" />
<pre>
<strong>Input:</strong> rectangles = [[0,0,2,2],[1,0,2,3],[1,0,3,1]]
<strong>Output:</strong> 6
<strong>Explanation:</strong> A total area of 6 is covered by all three rectangles, as illustrated in the picture.
From (1,1) to (2,2), the green and red rectangles overlap.
From (1,0) to (2,3), all three rectangles overlap.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> rectangles = [[0,0,1000000000,1000000000]]
<strong>Output:</strong> 49
<strong>Explanation:</strong> The answer is 10<sup>18</sup> modulo (10<sup>9</sup> + 7), which is 49.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= rectangles.length &lt;= 200</code></li>
	<li><code>rectanges[i].length == 4</code></li>
	<li><code>0 &lt;= x<sub>i1</sub>, y<sub>i1</sub>, x<sub>i2</sub>, y<sub>i2</sub> &lt;= 10<sup>9</sup></code></li>
	<li><code>x<sub>i1 &lt;= </sub>x<sub>i2</sub></code></li>
	<li><code>y<sub>i1 &lt;=</sub> y<sub>i2</sub></code></li>
</ul>

class Solution {
public:
    int rectangleArea(vector<vector<int>>& rectangles) {
        
        set<int> sx, sy;

        for( auto rec:  rectangles ){
            sx.insert(rec[0]);
            sx.insert(rec[2]);
            sy.insert(rec[1]);
            sy.insert(rec[3]);
        }

        map<int,int> x_i, y_i, i_x, i_y;
        int x = 0, y = 0; 
        
        for( int val:  sx )
            if( x_i.find(val)==x_i.end() ){
                i_x[x] = val;
                x_i[val] = x++;
            }

        for( int val:  sy )
            if( y_i.find(val)==y_i.end() ){
                i_y[y] = val;
                y_i[val] = y++;
            }
        
        vector<vector<int>> vis( x_i.size(), vector<int>(y_i.size(), 0) );
        int ans = 0, mod = 1e9 + 7;
        
        for( auto rec: rectangles )
            for( int i=x_i[rec[0]]+1; i<=x_i[rec[2]]; i++ )
                for( int j=y_i[rec[1]]+1; j<=y_i[rec[3]]; j++ )
                    if( !vis[i][j]++ ) ans = (ans + (1L*(i_y[j]-i_y[j-1])*(i_x[i]-i_x[i-1]))%mod)%mod;

        return ans;
    }
};
15500