<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) {
        int mod = 1e9+7;
        set<int> rows;
        set<int> cols;
        for(int i=0; i<rectangles.size(); i++){
            rows.insert(rectangles[i][0]);
            rows.insert(rectangles[i][2]);
            cols.insert(rectangles[i][1]);
            cols.insert(rectangles[i][3]);
        }
        unordered_map<int, int> rowmap;
        unordered_map<int, int> colmap;
        unordered_map<int, int> revRow;
        unordered_map<int, int> revCol;
        int index = 0;
        for(auto it = rows.begin();it!=rows.end();it++){
            rowmap[*it] = index;
            revRow[index] = *it;
            index++;
        }
        int nrows = index+1;
        index = 0;
        
        for(auto it = cols.begin(); it!=cols.end();it++){
            colmap[*it] = index;
            revCol[index] = *it;
            index++;
        }
        int ncols = index+1;
        vector<vector<int>> rects(nrows, vector<int>(ncols));
        for(int i=0; i<rectangles.size();i++){
            int startRow = rowmap[rectangles[i][0]];
            int endRow = rowmap[rectangles[i][2]];
            int startCol = colmap[rectangles[i][1]];
            int endCol = colmap[rectangles[i][3]];
            for(int j=startRow;j<endRow; j++){
                for(int k=startCol; k<endCol; k++){
                    rects[j][k] = 1;
                }
            }
        }
        // for(int i=0; i<rects.size();i++){
        //     for(int j=0; j<rects[0].size();j++){
        //         cout<<rects[i][j]<<" ";
        //     }
        //     cout<<endl;
        // }
        // cout<<endl;
        long long ans = 0;
        for(int i=0; i<rects.size();i++){
            for(int j=0; j<rects[0].size();j++){
                if(rects[i][j]==1){
                    long long area = ((((long long)revRow[i+1]-(long long)revRow[i])%mod) *(((long long)revCol[j+1]-(long long)revCol[j])%mod))%mod;
                    ans+= area%mod;
                    ans %= mod;
                }
            }
        }
        return ans;

    }
};
15000