December 2016
Intermediate to advanced
440 pages
9h 44m
Japanese
Content preview from アルゴリズムクイックリファレンス 第2版
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5.3
ハッシュに基づいた探索
■
117
ListElement
に貯えるため、追加の
12
バイトが必要となる。
213,557
語という前述
の例では、正味の文字列用ストレージを上回る
5,005,488
バイトのメモリが必要と
なる。その内訳は次のようになる。
●
基本となるハッシュ表のサイズ
1,048,572
バイト
●
116,186
個のリンク付きリストのサイズ
1,394,232
バイト
●
213,557
個のリスト要素のサイズ
2,562,684
バイト
JDK
のクラス
String
を用いるなら、文字列を貯えるのにもオーバーヘッドがか
かる。各文字列が
12
バイト余分に使うので、さらに
213,557*12
＝
2,562,684
バ
イトが余分に必要となる。この例で選んだアルゴリズムは、
7,568,172
バイトのメ
モリを必要とする。この例で用いた単語表の文字列の実際の文字数は、
2,099,075
にすぎない。したがって、このアルゴリズムは、文字列の文字数のほぼ
3.6
（＝
5,005,488/2,099,07
）倍のスペースを必要とする。
このオーバーヘッドの大半は、
JDK
のクラスを使うことによる。メモリ使用量を
減らすことのできるもっと複雑な実装と比較して、単純さとクラスの再利用をエン
ジニアリング上のトレードオフとして秤にかけなければならない。しかし、メモリ
が十分あるなら、衝突をあまり起こさない妥当なハッシュ関数とすぐに使えるリン
ク付きリストの実装という点で、
JDK
を用いるのは十分実用的だ。
実装に影響する肝心の点は ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
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.