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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82
■
4
章 整列アルゴリズム
4.4.4.4
小さな部分配列には、より単純な挿入ソート技法を用いる
小さな配列では、
挿入ソート
の方が
クイックソート
より速いが、大きな配列に用い
られた場合にも、
クイックソート
では、最終的に多数の小さな部分配列内を整列す
る必要がある。
クイックソート
の再帰性能を改善するために幅広く使われる技法の
1
つとして、例 4-6に示すように、大きな部分配列にだけ
クイックソート
を呼び出して、
小さな配列には
挿入ソート
を使うことが挙げられる。
Sedgewick
（
1978
）は、小さな部分配列に
median-of-three
と
挿入ソート
を組み合
わせ、純粋な
クイックソート
に比べて
20
〜
25
％の速度向上を引き出した。
4.4.4.5
イントロソート
小さな部分配列に対して、
挿入ソート
に切り替えるかどうかは、その部分配列の
サイズに基づいて局所的に決める。
Musser
（
1997
）は、イントロソート（
IntroSort
）
と呼ばれる
クイックソート
の変形を提案したが、これは、
クイックソート
の再帰の深
さを監視して効率的な処理を保証する。
クイックソート
の再帰の深さが
log (n)
を超
えると、
ヒープソート
に切り替える。
C
++
の標準テンプレートライブラリの
SGI
実
装では、イントロソートをデフォルトの整列メカニズムとしている（
http:
//
www.
sgi.com
/
tech
/
stl
/
sort.html
）。
4.5
比較なしの整列
本章の最後で、比較ベースの整列アルゴリズムが、
n
個の要素を
O(n log ...
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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.