<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>>& a) {
        const int mod = 1e9 + 7;
        // chia ra các khoảng theo Oy -> tối đa 400 khoảng
        set<int> st;
        for(auto&x:a) {
            st.insert(x[1]);
            st.insert(x[3]);
        }
        vector<int> b;
        for(auto&x:st) b.push_back(x);
        // For từng khoảng, duyetj hết các khối để đánh dáu
        int res = 0;
        for(int i=0; i<b.size()-1; i++) {
            // duyệt lại xem đánh dấu được bao nhiêu x  _. nhân với khoảng là ra dienj tích khoảng này
            int dy = b[i+1] - b[i];
            map<int,int> mp;
            for(auto&x:a) {
                if(x[3] <= b[i] || x[1]>=b[i+1]) continue;
                mp[x[0]]++;
                mp[x[2]]--;
            }
            int sum = 0;
            for(auto&[x,y]:mp) {
                sum += y;
                mp[x] = sum;
            }
            int fi = INT_MAX;
            for(auto&[x,y]:mp) {
                if(y==0) {
                    if(fi!=INT_MAX) res = (res+(1ll*(x-fi)*dy)%mod)%mod;
                    fi = INT_MAX;
                } else {
                    fi = min(fi, x);
                }
            }
        }
        return res;
    }
};
18400