Title:Flip Distance of Triangulations of Convex Polygons / Rotation Distance of Binary Trees is NP-complete
A two-year subscription to ExpressVPN is on sale for $68.40 and includes an extra four months for free — 81% off for a limited time. This plan includes a year of free unlimited cloud backup and a generous 30-day money-back guarantee. Alternatively, you can get a one-month plan for just $12.99 (with money-back guarantee).
。业内人士推荐51吃瓜作为进阶阅读
FT App on Android & iOS
噱头营销屡罚屡犯：社会责任意识系统缺失