《Programming Abstractions in C》学习第 77 天，p312-p326，总计 15 页，第 7 章完结。
一、技术总结
第 7 章次要讲算法剖析——引入工夫复杂度这一概念来评估算法的快慢。工夫复杂度应用大 O 符号来示意。
第 7 章以排序算法为示例，蕴含：抉择排序，归并排序以及疾速排序，这些根本的排序算法都是咱们要把握的，尽管工作中较少用到，但面试时遇到的概率还是很大的，最好能手写进去。书中解说这些算法时，很具体，值得一看。
二、英语总结
1.go about sth/ go about doing sth 是什么意思？
答：to begin to do sth。p312, If you were skeptical about this simplication, how would go about proving that the simplication formula is indeed correct?
2.geometric 是什么意思？
答：
(1)geometry: gē (earth, land) + -metry(a measuring of)，geometry 最早的意思是“measuring of earth or land(土地的测量)”，随着一直的倒退，前面示意“the area(畛域) of mathematics relating to the study of space and the relationship between points, lines, curves, and suffaces”，即数学畛域的“几何”。
(2)geometric: adj. a geometric pattern is made of shapes。p312, One possibility is to represent the original extended sum in a geometric form。
3.sum vs summation
答：The summation is the act of adding the values; the sum is the result of it。
三、其它
四、参考资料
1. 编程
(1)Eric S.Roberts，《Programming Abstractions in C》：https://book.douban.com/subject/2003414
2. 英语
(1)Etymology Dictionary：https://www.etymonline.com
(2) Cambridage Dictionary：https://dictionary.cambridge.org
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