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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98
｜
第
5
章
•
散列表
H
存储着集合
C
的
n
个元素。在
A
中有
b
个桶。
•
散列函数
hash
，根据
e
来计算出一个整数索引
h
（
0
≤
h
<
b
）。
n>7߲
ᇮ໎
ऺ໙
॰ኵ
ऺ໙Aዐڦොଚᆅ
h=hash)e*ǖፌܠᅜ
ᆶb>5߲փཞڦརă
ၜ2ǖ๑ᆩ૾
ၜ3ǖਸݣۨ
؋ॽࣷڞዂ
ᇮ໎ԥݣڟփཞ
ڦ࿋ዃ
图 5-1：散列的一般步骤
使用数组和链表将这些信息存储在内存中。
当实现
散列搜索
时，有两个需要注意的地方：散列函数的设计以及如何处理冲突。
设计不当的散列函数可能会导致不均匀的散列值分布。这样会导致两个结果：①散列表
中的很多桶没有被利用，浪费了空间。②使用中的桶又会因多个键值同时映射到了一个
桶中而导致大量的冲突，这使得性能更加糟糕。
5.3.1 输入 / 输出
与
二分搜索
不同，在
散列搜索
中，原始集合
C
不需要是有序的。不仅如此，即便
C
有序，
散列函数在插入散列表
H
时也不会尝试去保持其有序性。
散列搜索
的输入是散列表
H
，以及待查找的目标元素
t
。其输出也和其他搜索算法一样，
存在即返回
true
，否则
返回
false
。
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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.