本来这不是我现在该想的东西，被迫因为建模比赛看了一点。所学东西太过杂乱。 为什么不用Matlab、Mathematica 因为Mathematica被我卸了，Matlab没学过，也不喜欢。这只是一个排除法，我不知道该怎么从优势上比较。 R语言没学过，Julia也没有，所以回归工具齐全的Python。 Python 数据分析套装 建议目标就是分析数据的人直接安装anaconda，使用jupyte

树链剖分可以用来维护树上路径的信息。把树上的节点拆成不超过O(log⁡n)O(\log n)O(logn)段连续的路径（链），以映射到线段树或者什么的构来维护数据。 依照子树的大小，将最大子树作为重边，其他子树作为轻边，从而在树上拆分出多条链。为同一条链上的节点连续编号，完成剖分。至于剩下的，依照编号一条链可以连续的映射到数据结构的某个取间内，用类似于倍增LCA的方法在树上得到每一个询问所覆盖的链

Ivan plays a computer game that contains some microtransactions to make characters look cooler. Since Ivan wants his character to be really cool, he wants to use some of these microtransactions — and

You have a bag which contains n cards. There is a number written on each card; the number on i-th card is ai.

You are given a tree

把先前信息低的两篇blog给拆了,这样好点.

C 无脑DP.设状态f(i,j,0/1)f(i,j,0/1)f(i,j,0/1)表示已经设置了iii位,用了jjj个偶数,第iii位是偶数/奇数.然后 f(i,j,0)=min⁡{f(i−1,j−1,0),f(i−1,j−1,1)+1}f(i,j,1)=min⁡{f(i−1,j,0)+1,f(i−1,j,1)}\begin{aligned} f(i,j,0)&=\min\{f(i-1,j

Today, as a friendship gift, Bakry gave Badawy n integers a1,a2,…,an and challenged him to choose an integer X such that the value max1≤i≤n(ai⊕X) is minimum possible, where ⊕ denotes the bitwise XOR o

例题-4 HDU2089 不要62 统计数位中没有出现4和62的数字个数。 分析 不要4，可以在4时直接不转移。对于62，可以维护一个上一个数字填了啥，就可以像4一样判断了。

Liaoning ship, which named after a province of China, is the first aircraft carrier commissioned into the People’s Liberation Army Navy. It was bought from Ukraine as a stripped hulk and was rebuilt b