2-sat问题 留坑码住！！

遇到2-sat问题始于这个题目
CF228E The Road to Berland is Paved With Good Intentions

还没实现代码，先留坑

留下学习链接：
https://wenku.baidu.com/view/afd6c436a32d7375a41780f2.html

https://blog.youkuaiyun.com/jarjingx/article/details/8521690

还有这个的小说明：
https://blog.youkuaiyun.com/weixin_30750335/article/details/96993061?depth_1-utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromBaidu-1&utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromBaidu-1