<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 {
#define MOD 1000000007
public:
    int rectangleArea(vector<vector<int>>& rectangles) {
        map<int, vector<vector<int>>> events;
        map<int, int> line;

        for (auto& rec: rectangles) {
            vector<int> temp{1, rec[1], rec[3]};
            events[rec[0]].push_back(temp);
            temp[0] = -1;
            events[rec[2]].push_back(temp);
        }

        long long prev_x = -1, y_sum = 0;
        long long ans = 0;
        for (auto& iter: events) {
            if (prev_x != -1) {
                ans = (ans + (iter.first - prev_x)*y_sum) % MOD;
            }
            for (auto& event: iter.second) {
                if (event[0] == 1) {
                    line[event[1]]++;
                    line[event[2]]--;
                } else {
                    line[event[1]]--;
                    line[event[2]]++;
                }
            }

            y_sum = 0;
            int cur = 0, prev = 0, start = -1;
            for (auto& it: line) {
                if (cur == 0) {
                    start = it.first;
                }
                cur += it.second;
                if (cur == 0 && start != -1) {
                    y_sum += it.first - start;
                    start = -1;
                }
            }

            prev_x = iter.first;
        }

        return (ans < 0) ? ans + MOD : ans%MOD;
    }
};
12600