我在Ruby(1.9.3)中有一个数组,其中每个元素描述了一个机场的几个参数:
@airport_array = Array.new
@airports.each do |airport|
@airport_array.push({:id => airport.id, :iata_code => airport.iata_code, :city => airport.city, :country => airport.country})
end
特别是:city
和:country
都是字符串,我希望能够按字母顺序按字母顺序排序,然后按字母顺序排列。
我能够使用类似的东西对整数进行排序:
@airport_array = @airport_array.sort_by {|airport| [-airport[:country], airport[:city]]}
但是,这种语法(特别是使用 - 符号表示反向排序)似乎不适用于字符串。我收到以下错误:
undefined method `-@' for "United States":String
如果我删除减号,我不会收到错误,但正如预期的那样,两个参数的排序都是按字母顺序排列的。
有没有办法可以用两个字符串对这个数组进行排序,只有一个字符串按反向字母顺序排列?
举个例子,假设我有以下数组:
[{:id=>1, :iata_code=>"SEA", :city=>"Seattle", :country=>"United States"},
{:id=>2, :iata_code=>"DEN", :city=>"Denver", :country=>"United States"},
{:id=>3, :iata_code=>"YVR", :city=>"Vancouver", :country=>"Canada"},
{:id=>4, :iata_code=>"HNL", :city=>"Honolulu", :country=>"United States"},
{:id=>5, :iata_code=>"YOW", :city=>"Ottawa", :country=>"Canada"},
{:id=>6, :iata_code=>"YHZ", :city=>"Halifax", :country=>"Canada"}]
在我对它进行排序之后,我希望得到以下数组:
[{:id=>2, :iata_code=>"DEN", :city=>"Denver", :country=>"United States"},
{:id=>4, :iata_code=>"HNL", :city=>"Honolulu", :country=>"United States"},
{:id=>1, :iata_code=>"SEA", :city=>"Seattle", :country=>"United States"},
{:id=>6, :iata_code=>"YHZ", :city=>"Halifax", :country=>"Canada"},
{:id=>5, :iata_code=>"YOW", :city=>"Ottawa", :country=>"Canada"},
{:id=>3, :iata_code=>"YVR", :city=>"Vancouver", :country=>"Canada"}]
所以这些国家是反向字母顺序(U,C),然后在一个国家内,城市按字母顺序排列(D,H,S和H,O,V)。
答案 0 :(得分:3)
我以为我会使用Enumerable#sort_by来解决这个问题,但我遇到了你所做的同样的问题,所以我使用了一个块。已知带有块的Enumerable#sort比sort_by慢,所以我很好奇别人怎么回答这个问题。
我使用了它:
arr.sort { |a, b| [b[:country], a[:city]] <=> [a[:country], b[:city]] }
看起来像这样:
[76] pry(main)> arr
=> [{:id=>1, :iata_code=>"SEA", :city=>"Seattle", :country=>"United States"},
{:id=>2, :iata_code=>"DEN", :city=>"Denver", :country=>"United States"},
{:id=>3, :iata_code=>"YVR", :city=>"Vancouver", :country=>"Canada"},
{:id=>4, :iata_code=>"HNL", :city=>"Honolulu", :country=>"United States"},
{:id=>5, :iata_code=>"YOW", :city=>"Ottawa", :country=>"Canada"},
{:id=>6, :iata_code=>"YHZ", :city=>"Halifax", :country=>"Canada"},
{:id=>2, :iata_code=>"DOV", :city=>"Dover", :country=>"United States"}]
[77] pry(main)> arr.sort { |a, b| [b[:country], a[:city]] <=> [a[:country], b[:city]] }
=> [{:id=>2, :iata_code=>"DEN", :city=>"Denver", :country=>"United States"},
{:id=>2, :iata_code=>"DOV", :city=>"Dover", :country=>"United States"},
{:id=>4, :iata_code=>"HNL", :city=>"Honolulu", :country=>"United States"},
{:id=>1, :iata_code=>"SEA", :city=>"Seattle", :country=>"United States"},
{:id=>6, :iata_code=>"YHZ", :city=>"Halifax", :country=>"Canada"},
{:id=>5, :iata_code=>"YOW", :city=>"Ottawa", :country=>"Canada"},
{:id=>3, :iata_code=>"YVR", :city=>"Vancouver", :country=>"Canada"}]
答案 1 :(得分:1)
这个答案应该被视为一种好奇心。它假定所有国家/地区名称都是一个单词。
arr = [
{:id=>1, :iata_code=>"SEA", :city=>"Seattle", :country=>"United States"},
{:id=>2, :iata_code=>"DEN", :city=>"Denver", :country=>"United States"},
{:id=>3, :iata_code=>"YVR", :city=>"Vancouver", :country=>"Canada"},
{:id=>4, :iata_code=>"HNL", :city=>"Honolulu", :country=>"United States"},
{:id=>5, :iata_code=>"YOW", :city=>"Ottawa", :country=>"Canada"},
{:id=>6, :iata_code=>"YHZ", :city=>"Halifax", :country=>"Canada"}]
arr.sort_by { |h| [-h[:country].downcase.to_i(36), h[:city]] }
#=> [{:id=>2, :iata_code=>"DEN", :city=>"Denver", :country=>"United States"},
# {:id=>4, :iata_code=>"HNL", :city=>"Honolulu", :country=>"United States"},
# {:id=>1, :iata_code=>"SEA", :city=>"Seattle", :country=>"United States"},
# {:id=>6, :iata_code=>"YHZ", :city=>"Halifax", :country=>"Canada"},
# {:id=>5, :iata_code=>"YOW", :city=>"Ottawa", :country=>"Canada"},
# {:id=>3, :iata_code=>"YVR", :city=>"Vancouver", :country=>"Canada"}]
答案 2 :(得分:0)
你可以使用你所在国家/地区第一个字母的ASCII值 - 使用String#ord
输出一个整数 - 用于反向排序要求,如下所示:
@airport_array.sort_by {|airport| [-airport[:country][0].ord, airport[:city]]}
编辑:此选项不保证以相同的字母开头的正确种类的不同国家,例如“柬埔寨”和“加拿大”,所以让我们在此技术的基础上考虑所有字母名字。
我想出了这个函数来获取给定字符串中的转置字,将转置字定义为ascii表中转置字母的总和(即'A'变为'Z','C'变为'X'等等,有效地获得一个单词,你可以按逆向字母顺序使用。
# For each upcased letter, transpose the letter according to the ascii table
# considering that 'A'.ord => 65 and 'Z'.ord => 90,
# using 65 - X + 90 to obtain the ascii value for the transposed letter.
#
# Usage examples:
# ascii_inverse('A') => 'Z'
# ascii_inverse('Denver') => "WVMEVI"
# ascii_inverse('DENVER') => "WVMEVI"
def ascii_inverse(text)
text.upcase.chars.map{ |char| (155 - char.ord).abs }.map(&:chr).join
end
现在,您可以将此方法用于sort_by
语句:
@airport_array.sort_by {|airport| [ascii_inverse(airport[:country]), airport[:city]]}
最后,我要说我认为这只是一个练习,看看我走多远这条路。虽然它有效但我不愿意使用这种方法,除非有明显的性能优势而且我需要它,而且我可能会更简单的@ Anthony的sort
方法。