8.1

https://oi-wiki.org/math/linear-algebra/basis/
https://www.luogu.com.cn/article/t2zqvdou
https://oi-wiki.org/dp/opt/slope-trick/
https://www.cnblogs.com/Xing-Ling/p/11317315.html
https://www.bilibili.com/video/BV1gohHzkEHy/?spm_id_from=333.1007.top_right_bar_window_history.content.click&vd_source=3a2eaca74fd6bf9c2eb73aff6aaea30b t1 ksk重构树
补题 找u盘装回来东西