检查是否数组已经排序？ [英] Check to see if an array is already sorted?

问题描述

我知道如何的把的为了一个阵列，但在这种情况下，我只是想看看它的是的秩序。字符串数组是最简单的，我想，并在这一方面的回答美联社preciated，但包括检查依据一些任意参数顺序的能力，答案是最优的。

I know how to put an array in order, but in this case I just want to see if it is in order. An array of strings would be the easiest, I imagine, and answers on that front are appreciated, but an answer that includes the ability to check for order based on some arbitrary parameter is optimal.

下面是一个例子的数据集。名称：

Here's an example dataset. The name of:

[["a", 3],["b",53],["c",2]]

当元件是本身包含几个元件，其中第一个是一个字符串数组。我想看看如果这些元素基于此字符串按字母顺序排列。

Where the elements are themselves arrays containing several elements, the first of which is a string. I want to see if the elements are in alphabetical order based on this string.

推荐答案

让我们打开可枚举对于这样一个通用的抽象：

Let's open Enumerable for such a generic abstraction:

module Enumerable
  def sorted?
    each_cons(2).all? { |a, b| (a <=> b) <= 0 }
  end
end

[["a", 3], ["b", 53],["c", 2]].sorted? #=> true

公告称，不幸的是，我们必须写（A＆LT; =＆GT; B）＆LT; = 0 而不是 A＆LT; = b 因为有支持类＆LT; =＆GT; 但没有比较运营商（即阵列），因为它们不包括模块比较。

Notice that, unfortunately, we have to write (a <=> b) <= 0 instead of a <= b because there are classes that support <=> but not the comparator operators (i.e. Array), because they do not include the module Comparator.

您也说您想拥有检查基于一些任意参数顺序的能力。有了同样的想法：

You also said you'd like to have the ability "to check for order based on some arbitrary parameter". With the same idea:

module Enumerable  
  def sorted_by?
    each_cons(2).all? { |a, b| ((yield a) <=> (yield b)) <= 0 }    
  end
end

[["a", 3], ["b", 1], ["c", 2]].sorted_by? { |k, v| v } #=> false

使用懒惰可枚举（红宝石=> 2.1），它的好得多，我们可以重新使用我们的previous抽象可枚举＃分类写：

With lazy enumerables (Ruby => 2.1) it's much nicer, we can re-use our previous abstraction Enumerable#sorted? and write:

module Enumerable  
  def sorted_by?(&block)
    lazy.map(&block).sorted?
  end
end

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