《自动机理论、语言和计算导论》学习第 14 天，p428-p525 总结，总计 98 页。

一、技术总结

1.Kruskal's algorithm(克鲁斯克尔算法)

2.NP-Complete Problems

p434, We say L is NP-complete if the following statements are true about L:

(1)L is in NP。

(2)For every language L' in NP there is a polynomial-time reduction of L' to L。

3.QBF

quantified boolean formulas。

二、英语总结

1.couch

v. couch sth in/as sth: to express sth in a particular way。

eg: I don't understand this form- it's all couched in legal terminology。

2.conservatively

(1)conserve: con-(assimilated form of com-) + *ser-(to protect)。由“protect”引申出“maintain”之意。

(2)conservative: adj. not usually liking or trusting change, especially sudden change。

(3)conservatively: adv. in a way that is not fashionable.

3.deceptively

(1)deceive: vt. to persuade sb that sth false is the truth。

(2)deceptive：adj. misleading。

(3)deceptively: adv. in a way that is deceptive。

eg: The plan seemed deceptively simple(=it seemed simple but was not)。

4.permutation

(1)permute:per-(thoroughly) + mutare(to change)。vt. to change one for another。

eg: We wish to permute the order of the bytes。

(2)permutation: n. ways in which a set of things can be ordered(数学上的“排列”)。

eg: There are 120 permutations of the numbers 1, 2, 3, 4 and 5; for example, 1, 3, 2, 4,5 or 5, 1, 4, 2, 3。

5.slight

adj. small in amount or degree。Slight is sometimes used with abstract noun to describe amounts or degree of change that are small and not important。

6.adequate

ad-(to) + equal。adj. equal to what is needed or desired, sufficient； enough or satisfactory for a particular purpose。

7.instinct

in-(in) + stinguere(prick, goad)。n. the way people or animals naturally react without having to think or lean about it。

eg: Her first instinct was to run。

三、其它

历时 14 天，500 多页的《自动机理论、语言和计算导论》算是看完了，这些算是编译原理的前导知识，对自动机、正则表达式、语言、上下文无关语法、P 和 NP 问题有了一个初步的认识与了解，谈不上掌握，更谈不上深入。如果你问我书中的 xxx 习题怎么解，那我只能如实回答：不会。

每天发这些学习笔记，对读者而言，其实意义并不大，帮助很小。如果要说有什么意义，那么可能就是起到一个示例的作用，在编程这条路上，我在做什么，我是怎么做的。

虽然这些“基础”学起来很难，但我会努力，感谢那么久以来一直还关注的读者没有取关。

四、参考资料

1. 编程

(1)Eric S.Roberts，《自动机理论、语言和计算导论(英文版.第 3 版)》：https://book.douban.com/subject/2274854/

2. 英语

(1)Etymology Dictionary：https://www.etymonline.com

(2) Cambridge Dictionary：https://dictionary.cambridge.org

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