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April 29, 2012 14:57
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Rubyでアルゴリズムやらデータ構造やらのお勉強(Merge Sort)
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# -*- coding: utf-8 -*- | |
# Cで書かれたアルゴリズムやらデータ構造なりを、自分なりにRubyで表現してみるお勉強PJ。 | |
# 参考書籍(プログラミングの宝箱 アルゴリズムとデータ構造) | |
# Ruby1.9.3で動作確認済み | |
# と言っといてなんだけど、同書籍にCじゃなくJava版もあったので今度はそちらをもとにした。 | |
# ところがこれもというかなおさらというか読みやすくはない。 | |
# どちらにせよ1文字のカウンタ変数とか使われると、この広さはすでに読むのしんどいなー。 | |
# (古本で入手したんだけど、そもそもC版の方の変数名に前所有者の解説コメントが。ということはやっぱ直感的じゃないのでは) | |
# これも要見直し | |
$VERBOSE = true | |
class Array | |
def merge_sort! | |
_merge_sort! self, self.size, 0 | |
self | |
end | |
private | |
def _merge_sort!(list, block_size, offset) | |
return if block_size <= 1 | |
head_size = block_size / 2 | |
_merge_sort! list, head_size, offset | |
_merge_sort! list, block_size - head_size, offset + head_size | |
buffer = [] | |
(0...head_size).each do |n| | |
buffer[n] = list[offset + n] | |
end | |
j, i, pos = head_size, 0, 0 | |
while i < head_size && j < block_size | |
if buffer[i] <= list[offset + j] | |
list[offset + pos] = buffer[i] | |
i += 1 | |
else | |
list[offset + pos] = list[offset + j] | |
j += 1 | |
end | |
pos += 1 | |
end | |
(i...head_size).each do |n| | |
list[offset + pos] = buffer[n] | |
pos += 1 | |
end | |
end | |
end | |
# Overview | |
list = (-50..50).to_a.shuffle | |
p list | |
p list.object_id | |
p list.merge_sort! | |
p list.object_id |
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