推荐网址链接
关于spfa优化和判环
https://blog.****.net/liangzhaoyang1/article/details/62423135
https://blog.****.net/crybymyself/article/details/53165306
https://blog.****.net/corncsd/article/details/18411437
树的重心、直径等
https://blog.****.net/DOLEAM/article/details/70943678
差分约束系统
https://blog.****.net/consciousman/article/details/53812818
http://www.cppblog.com/menjitianya/archive/2015/11/19/212292.html
倍增求lca
https://blog.****.net/lw277232240/article/details/72870644
例题：暗象石https://blog.****.net/qq_25978793/article/details/49362505
洛谷日报：https://www.luogu.org/discuss/show/48491
Tarjan算法详解：https://blog.****.net/qq_34374664/article/details/77488976
史上最全的Tarjan模板：https://blog.****.net/chai_jing/article/details/70147646
洛谷日报：骗分技巧https://www.luogu.org/blog/52913/special-program
快速幂详解：https://wenku.baidu.com/view/d65f294702768e9951e73883.html