https://www.luogu.com.cn/problem/solution/P5490 P5490 【模板】扫描线 & 矩形面积并 https://www.bilibili.com/video/BV1MX4y1Z7N5/?spm_id_from=333.337.search-card.all.click&vd_source=516557f2525ba2ce9681cb21259ba063
C31 扫描线 P1856 [IOI1998] 矩形周长 https://www.luogu.com.cn/problem/P1856
https://www.bilibili.com/video/BV1F94y167AQ/?spm_id_from=333.337.search-card.all.click&vd_source=516557f2525ba2ce9681cb21259ba063
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