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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150
｜
第
6
章
实现做一些基准评测。在下面的表
6-1
中，我们执行了
9
次算法，并抛弃了最好和最坏
的结果，只展示了剩余
7
次结果的平均值。
6.6.1 基准测试数据
产生一个随机图是非常困难的。在表
6-1
中，我们使用的是有
|
V
| =
k
2
+ 2
个顶点，以及
|
E
| =
k
3
－
k
2
+ 2
k
条边的图（图的构造细节参见代码库中的实现）。注意
，边的数目大概
是
n
1.5
，其中
n
是顶点的数目。使用优先队列的
Dijkstra
算法
性能最好，
Bellman-Ford
算法
的性能次之。可以看到，针对稠密图优化的
Dijkstra
算法
性能较差。
表
6
-
1
：在基准图测试图上计算单源顶点最短路径的时间
V
/ 个
E
/ 条 使用优先队列的 针对稠密图优化的 Bellman-Ford 算法
Dijkstra 算法 Dijkstra 算法
6 8 0.000002 0.000002 0.000001
18 56 0.000004 0.000003 0.000001
66 464 0.000012 0.000018 0.000005
258 3,872 0.00006 0.000195 0.000041
1,026 31,808 0.000338 0.0030 0.000287
4,098 258,176 0.0043 0.0484 0.0076
16,386 2,081,024 0.0300 0.7738 0.0535
6.6.2 稠密图
在稠密图中，
E
大约是
O
(
V
2
)
阶，例如，在有着 ...
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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.