Reputation: 3
Ruby: how to sort array of string parsing the content
Here is my problem: I have an array of string which contains data like that:
array = ["{109}{08} OK",
"{98} Thx",
"{108}{0.8}{908} aa",
"{8}{51} lorem ipsum"]
I would like to sort this array scanning "data inside": here the integers in brace. So, the final array should be like that :
array.custom_sort! => ["{8}{51} lorem ipsum",
"{98} Thx",
"{108}{0.8}{908} aa",
"{109}{08} OK"]
Is there a nice solution to do it in Ruby? Or should I recreate a new array which inserts each parsed elements?
EDIT:
I failed to mention the sort priorities: First, the sorting is based on the number in braces, up to 3 groups, but cannot be absent.
["{5}something",
"{61}{64}could",
"{}be", #raise an error or ignore it
"{54}{31.24}{0.2}write",
"{11}{21}{87}{65}here", #raise an error or ignore it
"[]or", #raise an error or ignore it
"{31}not"]
If the first numbers are equal, then the second ones should be compared. Some examples:
"{15}" < "{151}" < "{151}{32}" < "{152}"
"{1}" < "{012}" < "{12}{-1}{0}" < "{12.0}{0.2}"
"{5}" < "{5}{0}" < "{5}{0}{1}"
But if every numbers are equals, then the string is compares. The only character which make a problem is the space, which must be after every other "visible" characters. Examples:
"{1}a" < "{1}aa" < "{1} a" < "{1} a"
"{1}" < "{1}a " < "{1}a " < "{1}a a"
"{1}a" < "{1}ba" < "{1}b "
I can make it doing somethign like this in a custom class:
class CustomArray
attr_accessor :one
attr_accessor :two
attr_accessor :three
attr_accessor :text
def <=>(other)
if self.one.to_f < other.one.to_f
return -1
elsif self.one.to_f > other.one.to_f
return 1
elsif self.two.nil?
if other.two.nil?
min = [self.text, other.text].min
i = 0
until i == min
if self.text[i].chr == ' ' #.chr is for compatibility with Ruby 1.8.x
if other.text[i].chr != ' '
return 1
end
else
if other.text[i].chr == ' '
return -1
#...
self.text <=> other.text
end
end
It works fine, but I am very frustrated coding in Ruby like I code in C++ project. That is why I would like to know how to use a "custom sort in a foreach method" with a more complexe sort way (require parsing, scanning, regexp) than a naive one based on an attribute of the content.
Upvotes: 0
Views: 208
Answers (4)
Reputation: 110755
[Edit: My initial solution, which follows this edit, does not work with the revised statement of the question. I will leave it, however, as it might be of interest regardless.
The following is a way to perform the sort under the revised rules, as I understand them. If I have misinterpreted the rules, I expect the fix would be minor.
Regex to use
Let's start with the regex I'll use:
R = /
\{ # match char
( # begin capture group
\d+ # match one or more digits
(?: # begin non-capture group
\. # match decimal
\d+ # match one or more digits
) # end non-capture group
| # or
\d* # match zero or more digits
) # match end capture group
\} # match char
/x
Examples:
a = ["{5}something", "{61}{64}could", "{}be", "{54}{31.24}{0.2}write",
"{11}{21}{87}{65}here", "[]or", "{31}not", "{31} cat"]
a.each_with_object({}) { |s,h| h[s] = s.scan(R).flatten }
# => {"{5}something" =>["5"],
# "{61}{64}could" =>["61", "64"],
# "{}be" =>[""],
# "{54}{31.24}{0.2}write"=>["54", "31.24", "0.2"],
# "{11}{21}{87}{65}here" =>["11", "21", "87", "65"],
# "[]or" =>[],
# "{31}not" =>["31"]
# "{31} cat" =>["31"]}
custom_sort method
We can write the method custom_sort as follows (change sort_by to sort_by! for custom_sort!):
class Array
def custom_sort
sort_by do |s|
a = s.scan(R).flatten
raise SyntaxError,
"'#{s}' contains empty braces" if a.any?(&:empty?)
raise SyntaxError,
"'#{s}' contains zero or > 3 pair of braces" if a.size.zero?||a.size > 3
a.map(&:to_f) << s[a.join.size+2*a.size..-1].tr(' ', 255.chr)
end
end
end
Examples
Let's try it:
a.custom_sort
#=> SyntaxError: '{}be' contains empty braces
Remove "{}be" from a:
a = ["{5}something", "{61}{64}could", "{54}{31.24}{0.2}write",
"{11}{21}{87}{65}here", "[]or", "{31}not", "{31} cat"]
a.custom_sort
#SyntaxError: '{11}{21}{87}{65}here' contains > 3 pair of braces
Remove "{11}{21}{87}{65}here":
a = ["{5}something", "{61}{64}could", "{54}{31.24}{0.2}write",
"[]or", "{31}not", "{31} cat"]
a.custom_sort
#=> SyntaxError: '[]or' contains zero or > 3 pair of braces
Remove "[]or":
a = ["{5}something", "{61}{64}could", "{54}{31.24}{0.2}write",
"{31}not", "{31} cat"]
a.custom_sort
#=> ["{5}something",
# "{31}not",
# "{31} cat",
# "{54}{31.24}{0.2}write", "{61}{64}could"]
Explanation
Suppose one of the strings to be sorted was:
s = "{54}{31.24}{0.2}write a letter"
Then in the sort_by block, we would compute:
a = s.scan(R).flatten
#=> ["54", "31.24", "0.2"]
raise SyntaxError, "..." if a.any?(&:empty?)
#=> raise SyntaxError, "..." if false
raise SyntaxError, "..." if a.size.zero?||a.size > 3
#=> SyntaxError, "..." if false || false
b = a.map(&:to_f)
#=> [54.0, 31.24, 0.2]
t = a.join
#=> "5431.240.2"
n = t.size + 2*a.size
#=> 16
u = s[n..-1]
#=> "wr i te"
v = u.tr(' ', 255.chr)
#=> "wr\xFFi\xFFte"
b << v
#=> [54.0, 31.24, 0.2, "wr\xFFi\xFFte"]
Note that the use of String#tr (or you could use String#gsub) puts spaces at the end of the sort order of ASCII characters:
255.times.all? { |i| i.chr < 255.chr }
#=> true
tidE]
I have assumed that, in sorting, pairs of strings are to be compared in a manner analogous to Array#<=>. The first comparison considers the strings of digits within the the first pair of braces in each string (after conversion to a float). Ties are broken by comparing the strings of digits in the second pairs of braces (converted to floats). If there is still a tie, the third pairs digits enclosed in braces are compared, etc. If one string has n pairs of braces and another has m > n pairs, and the values within the braces are the same for the first n pairs, I assume the first string is to precede the second in the sort.
Code
R = /
\{ # match char
(\d+) # capture digits
\} # match char
+ # capture one or more times
/x
class Array
def custom_sort!
sort_by! { |s| s.scan(R).map { |e| e.first.to_f } }
end
end
Example
array = ["{109}{08} OK",
"{109}{07} OK",
"{98} Thx",
"{108}{0.8}{908} aa",
"{108}{0.8}{907} aa",
"{8}{51} lorem ipsum"]
a = array.custom_sort!
#=> ["{8}{51} lorem ipsum",
# "{98} Thx",
# "{108}{0.8}{907} aa",
# "{108}{0.8}{908} aa",
# "{109}{07} OK",
# "{109}{08} OK"]
array == a
#=> true
Explanation
Let's now calculate the value in Array#sort_by!'s block for the first element of array
s = "{109}{08} OK"
a = s.scan(R)
#=> [["109"], ["08"]]
b = a.map { |e| e.first.to_f }
#=> [109.0, 8.0]
Let's now do the same for the other strings and put the results in an array:
c = array.map { |s| [s, s.scan(R).map { |e| e.first.to_f }] }
#=> [["{8}{51} lorem ipsum", [8.0, 51.0]],
# ["{98} Thx", [98.0]],
# ["{108}{0.8}{907} aa", [108.0, 907.0]],
# ["{108}{0.8}{908} aa", [108.0, 908.0]],
# ["{109}{07} OK", [109.0, 7.0]],
# ["{109}{08} OK", [109.0, 8.0]]]
sort_by in custom_sort! is therefore equivalent to:
c.sort_by(&:last).map(&:first)
#=> ["{8}{51} lorem ipsum",
# "{98} Thx",
# "{108}{0.8}{907} aa",
# "{108}{0.8}{908} aa",
# "{109}{07} OK",
# "{109}{08} OK"]
Upvotes: 1
Reputation: 3041
array.sort_by { |v| (v =~ /(\d+)/) && $1.to_i }
alternately
array.sort_by { |v| /(\d+)/.match(v)[1].to_i }
Upvotes: 1
Reputation: 13541
This should do it:
array.sort_by do |s|
# regex match the digits within the first pair of curly braces
s.match(/^\{(\d+)\}/)[1].to_i # convert to an int in order to sort
end
# => ["{8}{51} lorem ipsum", "{98} Thx", "{108}{0.8}{908} aa", "{109}{08} OK"]
Upvotes: 1
Reputation: 483
You can pass Array#sort a block defining how it should order elements.
Upvotes: -2
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