《算法导论(第4版)》学习第 18 天，p83-p85 总结，总计 3 页。
一、技术总结
1. Strassen algorithm(施特拉森算法)
2.矩阵
(1)矩阵表示法
If we wish to refer to matrices without specifically writing out all their entries, we will use uppercase A, B, C, and so on. In general, aᵢⱼ will denote the entry of the matrix A that is in the ith row and the jth column. We will refer to this entry as the (i, j) entry of A. We will sometimes shorten this to A = (aᵢⱼ). Similarly, a matrix B may be referred to as (bᵢⱼ), a matrix C as (cᵢⱼ), and so on.
(2)dense matrix(密集矩阵) & sparse matrix(稀疏矩阵)、
Generally, we'll assume that the matrices are dense, meaning that most of the n² entries are not 0, as opposed to sparse, where most of the n² entries are 0 and the nonzero entries can be stored more compactly than in an n × n array.
二、英语总结(生词：0)
无。
关于英语的注解同步更新汇总到 https://github.com/codists/English-In-CS-Books 仓库。
三、其它
今天没有什么想说的。
四、参考资料
1. 编程
(1) Thomas H. Cormen，Charles E. Leiserson，Ronald L. Rivest，Clifford Stein，https://book.douban.com/subject/35591269/
2. 英语
(1) Etymology Dictionary：https://www.etymonline.com
(2) Cambridge Dictionary：https://dictionary.cambridge.org
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