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week1的第三题体现出函数式语言的优美
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Zang MingJie  
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 More options Oct 8 2012, 4:16 am
From: Zang MingJie <zealot0...@gmail.com>
Date: Mon, 8 Oct 2012 01:16:59 -0700 (PDT)
Local: Mon, Oct 8 2012 4:16 am
Subject: week1的第三题体现出函数式语言的优美
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递归+一个mapreduce就搞定了

  def countChange(money: Int, coins: List[Int]): Int = if (coins.isEmpty) {
    if (money == 0) 1 else 0
  } else {
    val cur = coins.head
    (0 /: ((0 to (money / cur)) map { i => countChange(money - i * cur,
coins.tail) })) { _ + _ }
  }


 
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颜发明  
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 More options Oct 10 2012, 3:37 am
From: 颜发明 <yfam...@gmail.com>
Date: Wed, 10 Oct 2012 00:37:00 -0700 (PDT)
Subject: Re: week1的第三题体现出函数式语言的优美
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我在这题上悲催了。绞尽脑汁也想不出一个好的递归方式，最后不伦不类地拼凑了一个既有递归又有while循环和var变量的怪异混合体，结果没问题，但是很丑陋 的说。
经由这一道一道的题目，慢慢地体会函数式的思想，现在找到一点点感觉了，小小进步中……

在 2012年10月8日星期一UTC+8下午4时16分59秒，Zang MingJie写道：


 
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Cheng CHI  
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 More options Oct 18 2012, 3:40 pm
From: Cheng CHI <cloudr...@gmail.com>
Date: Thu, 18 Oct 2012 12:40:43 -0700 (PDT)
Local: Thurs, Oct 18 2012 3:40 pm
Subject: Re: week1的第三题体现出函数式语言的优美
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最后的else里这样就可以了…… 不过前边也有一点点点不同…… (不直接发全部代码了@。@

  countChange(money, coins.tail) + countChange(money-coins.head, coins)


 
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Lurga Lee  
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 More options Oct 18 2012, 9:32 pm
From: Lurga Lee <lurga....@gmail.com>
Date: Fri, 19 Oct 2012 09:32:08 +0800
Local: Thurs, Oct 18 2012 9:32 pm
Subject: Re: [ScalaCN] Re: week1的第三题体现出函数式语言的优美
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这不是尾递归，在实际运行时很危险。昨天翻到个不错的文章【1】，十五章到十九章很好的解释了老师不停强调的递归和list（2,3,4,5课都能看到它的影子 ）
【1】http://buaawhl.iteye.com/blog/1160327

2012/10/19 Cheng CHI <cloudr...@gmail.com>


 
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杨博  
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 More options Oct 19 2012, 8:26 am
From: 杨博 <pop.a...@gmail.com>
Date: Fri, 19 Oct 2012 05:26:48 -0700 (PDT)
Local: Fri, Oct 19 2012 8:26 am
Subject: Re: week1的第三题体现出函数式语言的优美
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你这代码不符合Scala编码规范（http://docs.scala-lang.org/style/method-invocation.html）：

> Finally, the use of the /: and :\ should be avoided in preference to the
> more explicit foldLeftand foldRight method of Iterator. The
> right-associativity of the /: can lead to extremely confusing code, at
> the benefit of saving a few characters.

在 2012年10月8日星期一UTC+8下午4时16分59秒，Zang MingJie写道：


 
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