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
｜
43
算法基础
表
3
-
4
：特殊的 IEEE
754
值
特殊值
64
位 IEEE
754
表示
正无穷
0x7ff0000000000000L
负无穷
0x7ff0000000000000L
非数
（
NaN
）
从
0x7ff0000000000001L
到
0x7fffffffffffffffL
以及从
0xfff0000000000001L
到
0xffffffffffffffffL
负零
0x8000000000000000
正零
0x0000000000000000
这些特殊值是异常发生时返回的结果。例如，正无穷在
Java
中会作为
double
x=1/0.0
的结果。但有趣的是，如果这个表达式换成
double
x=1/0
，
Java
虚拟机将会抛出
ArithmeticException
异常，因为这个表达式是计算两个整数而不是浮点数的除法。
3.5 算法举例
我们将通过
Graham
扫描算法来介绍本书的算法模板。该算法可以用于计算二维空间上
给定点集的凸包（第
1
章已经介绍过这个问题，并在图
1-3
中予以说明）。
3.5.1 算法名称和摘要
Graham
扫描算法可以计算出笛卡儿空间给定点集的凸包。它首先会寻找输入集
P
中的
最低点
low
，然后将剩下的点
{
P
-
low
}
按照和
low
的极角从大到小排序。之后算法会按
序遍历这些点构建凸包，如果凸包上最新的三个点构成一个左拐，那么最新加入的点就
需要被删除掉。
3.5.2 输入 / 输出
凸包问题实例由一个点集
P
定义。
输出是一系列的（
x
,
y
）点，即顺时针输出凸包上的点。哪个点在最前面并不重要。 ...
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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.