Is it easier to get educated?

TOEFL Writing assignment, 2018 summer.

Education is influencing more people than it did in the past, with better quality and quantity. But many people think that it is much harder to get educated now than it did in the past. However, I cannot agree with them.

Firstly, it is much easier to get into the university. Though the tuition is much higher in the past, the average family income is more. In another words, we have much more income to pay the university expanses with a little increase. Students who are really unable to pay the university tuition can make a loan from the bank. There are no worries about the tuition. Also, the university recruits more students instead of a small part of people, the university education is no longer exclusive for the rich families. There are even new standards of entering to the university and laws to provide fairness. So, it is absolutely wrong that it is hard to get into the universities.

Secondly, many people are also worried about the elementary education. In China and many other countries, the compulsory education is provided for children. With the compulsory education, tuitions and other stuff about education are free, parents are not going to worry about the educational expanse. Furthermore, in some parts of China, the high school education is free. Also, the Chinese Government spends money aiding students with economical problems. There are many policies to enable minorities people to get educated more easily. Comparatively, there were even not words called “compulsory education”. Therefore, elementary education, without doubt, is easier to acquire now.

What is more, the higher technology enables people to attain good education resources instantly. Many websites like Coursera and Khan Academy, are promoting the educational open for the remote students. And students sitting in the classroom can also learn using iPads and Virtual Reality, illustrating vividly. People are paying more attention to the education and treating it as the first priority. Many universities are recording class to the public on the Internet, so that students from all over the world can learn knowledge without barriers.

In conclusion, students are living in a better era with more educational promotions. The modern technologies, the policies and laws, the financial progress enable us to study more efficiently than it did in the past. Therefore, without doubt, students can attain education more conveniently.

P4899:[IOI2018] werewolf 狼人题解

解法

这道题是 Kruskal 重构树的裸题。我们先来考虑从\(s\)出发的人形状态,我们要找到一个点点权小于\(L\)的点,就相当于在 Kruskal 重构树上倍增找到最后一个小于\(L\)的点。我们把符合人形规律的 Krukskal 树记为 Tl,其中构造它的方式就是把原来图上所有边的边权赋值为端点的最大值,然后按最小生成树的方式去构造重构树;符合狼形规律的 Kruskal 重构树被记为 Tu,其中构造它的方式就是将端点编号最小值赋为边权,然后按最大生成树的方式构造。之后,我们再到主席树中求交集即可,如果有交集那么查询结果为一个不为零的数,输出\(1\)即可;没有交集那么查询结果即为\(0\),输出\(0\)。

继续阅读P4899:[IOI2018] werewolf 狼人题解

主席树总结

简述

主席树是一个很有意思的数据结构,其全称其实是「可持久化线段树」,至于为什么叫「主席树」是因为:

由于发明者黄嘉泰姓名的缩写与前中共中央总书记、国家主席胡锦涛(H.J.T.)相同,因此这种数据结构也可被称为总书记树或主席树。

From Wikipedia.org

继续阅读主席树总结

Kruskal 重构树

简述

Kruskal 重构树是图的一种生成树,主要解决一类路径边权限制问题。Kruskal 重构树有按深度单调的性质,所以很容易就可以解决边权的取值限制。

建法

Kruskal 重构树的建造方法和 Kruskal 算法建最小生成树的方法非常类似,但是结构有所不同:Kruskal 重构树将边权变成点权,点权依深度变小。我们假设有一张这样的图:

继续阅读Kruskal 重构树