August 2017
Intermediate to advanced
360 pages
8h 35m
Chinese
Content preview from 算法技术手册（原书第2 版）
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算法基础
｜
39
算法基础
顺序搜索小结
最好情况：
O
(1)
平均情况和最坏情况：
O
(
n
)
search (A,t)
for i=0 to n-1 do
❶
if A[i] = t then
return true
return false
end
❶
按照从
0
到
n
－
1
的顺序访问每个元素。
ቴڟᇮ໎
࿄ݡ࿚ڦᇮ໎ݡ࿚ࡗڦᇮ໎
图 3-1：顺序搜索运行过程
3.3 实验评估的格式
我们会通过一系列的测试数据来确认算法的性能。关于性能测试流程的更多细节可以参
见附录
A
。一般来说，为了更加精确地评估性能，所使用的测试集会包含
k
个独立的测
试单元（一般
k
≥
10
）。最好和最坏的结果将被作为异常值抛弃，剩余的
k
- 2
次实验结
果会综合在一起，然后计算出平均值和标准差。我们会列出一张表，标明测试单元的规
模
n
（
n
的范围从
2~2
20
）。
3.4 浮点计算
由于书中的某些算法需要使用到数值计算，因此这里需要简单讲述一下现代计算机在数
值计算中的作用以及某些先天不足。众所周知，计算机是对存储在
CPU
寄存器的值进行
一些基本运算。随着计算机架构从
20
世纪
70
年代流行的
8
位
Intel
处理器演进到如今
广泛存在的
64
位架构（如
Intel
的
Itanium
以及
Sun
的
Sparc
处理器），寄存器的大小
也随之发生了翻天覆地的变化。
CPU
通常支持对存储在寄存器的整数进行一些基本的运
算，例如
ADD
、
MULT
、
DIVIDE
和
SUB
。浮点计算则交给了浮点运算单元（
FPU
）按
照
IEEE
关于二进制浮点算术的标准（ ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.