Lets say that I have an array of words, such as this:
words = ["apple", "zebra", "boat", "dog", "ape", "bingo"]
and I want to sort them alphabetically , but group them like so:
sorted = [["ape", "apple"], ["bingo", "boat"], ["dog"], ["zebra"]]
How would I be able to do this in Ruby? Help appreciated.
I'm assuming that you are trying to group by the first letter of each word. In which case you can use sort to sort the array and group_by to group by the first character of each word (as returned by chr).
words = ["apple", "zebra", "boat", "dog", "ape", "bingo"]
sorted = words.sort.group_by(&:chr).values
You could do something like this:
words.sort.chunk { |s| s[0] }.map(&:last)
This first sorts the array alphabetically (.sort), then it "chunks" together elements with the same first character (.chunk { |s| s[0] }), then it grabs the last element from each sub-array .map(&:last).
Something like this should do the trick
words = ["apple", "zebra", "boat", "dog", "ape", "bingo"]
sorted = words.sort.group_by { |s| s[0] }.map { |k,v| v }
You're going to need an array that also represents your categories. In this case, the letters of the alphabet. Below does what you're looking for using nested loops.
words = ["apple", "zebra", "boat", "dog", "ape", "bingo"]
results = []
('a'..'z').to_a.each_with_index do |letter, index|
letter_result = []
words.each do |word|
if(word[0]==letter)
letter_result.push(word)
end
end
unless letter_result.empty?
results.push(letter_result)
end
end
Related
I have read the xls and have formed these three hashes
hash1=[{'name'=>'Firstname',
'Locator'=>'id=xxx',
'Action'=>'TypeAndWait'},
{'name'=>'Password',
'Locator'=>'id=yyy',
'Action'=>'TypeAndTab'}]
Second Hash
hash2=[{'Test Name'=>'Example',
'TestNumber'=>'Test1'},
{'Test Name'=>'Example',
'TestNumber'=>'Test2'}]
My Thrid Hash
hash3=[{'name'=>'Firstname',
'Test1'=>'four',
'Test2'=>'Five',
'Test3'=>'Six'},
{'name'=>'Password',
'Test1'=>'Vicky',
'Test2'=>'Sujin',
'Test3'=>'Sivaram'}]
Now my resultant hash is
result={"Example"=>
{"Test1"=>
{'Firstname'=>
["id=xxx","four", "TypeAndWait"],
'Password'=>
["id=yyy","Vicky", "TypeAndTab"]},
"Test2"=>
{'Firstname'=>
["id=xxx","Five", "TypeAndWait"],
'Password'=>
["id=yyy","Sujin", "TypeAndTab"]}}}
I have gotten this result, but I had to write 60 lines of code in my program, but I don't think I have to write such a long program when I use Ruby, I strongly believe some easy way to achieve this. Can some one help me?
The second hash determines the which testcase has to be read, for an example, test3 is not present in the second testcase so resultant hash doesn't have test3.
We are given three arrays, which I've renamed arr1, arr2 and arr3. (hash1, hash2 and hash3 are not especially good names for arrays. :-))
arr1 = [{'name'=>'Firstname', 'Locator'=>'id=xxx', 'Action'=>'TypeAndWait'},
{'name'=>'Password', 'Locator'=>'id=yyy', 'Action'=>'TypeAndTab'}]
arr2 = [{'Test Name'=>'Example', 'TestNumber'=>'Test1'},
{'Test Name'=>'Example', 'TestNumber'=>'Test2'}]
arr3=[{'name'=>'Firstname', 'Test1'=>'four', 'Test2'=>'Five', 'Test3'=>'Six'},
{'name'=>'Password', 'Test1'=>'Vicky', 'Test2'=>'Sujin', 'Test3'=>'Sivaram'}]
The drivers are the values "Test1" and "Test2" in the hashes that are elements of arr2. Nothing else in that array is needed, so let's extract those values (of which there could be any number, but here there are just two).
a2 = arr2.map { |h| h['TestNumber'] }
#=> ["Test1", "Test2"]
Next we need to rearrange the information in arr3 by creating a hash whose keys are the elements of a2.
h3 = a2.each_with_object({}) { |test,h|
h[test] = arr3.each_with_object({}) { |f,g| g[f['name']] = f[test] } }
#=> {"Test1"=>{"Firstname"=>"four", "Password"=>"Vicky"},
# "Test2"=>{"Firstname"=>"Five", "Password"=>"Sujin"}}
Next we need to rearrange the content of arr1 by creating a hash whose keys match the keys of values of h3.
h1 = arr1.each_with_object({}) { |g,h| h[g['name']] = g.reject { |k,_| k == 'name' } }
#=> {"Firstname"=>{"Locator"=>"id=xxx", "Action"=>"TypeAndWait"},
# "Password"=>{"Locator"=>"id=yyy", "Action"=>"TypeAndTab"}}
It is now a simple matter of extracting information from these three objects.
{ 'Example'=>
a2.each_with_object({}) do |test,h|
h[test] = h3[test].each_with_object({}) do |(k,v),g|
f = h1[k]
g[k] = [f['Locator'], v, f['Action']]
end
end
}
#=> {"Example"=>
# {"Test1"=>{"Firstname"=>["id=xxx", "four", "TypeAndWait"],
# "Password"=>["id=yyy", "Vicky", "TypeAndTab"]},
# "Test2"=>{"Firstname"=>["id=xxx", "Five", "TypeAndWait"],
# "Password"=>["id=yyy", "Sujin", "TypeAndTab"]}}}
What do you call hash{1-2-3} are arrays in the first place. Also, I am pretty sure you have mistyped hash1#Locator and/or hash3#name. The code below works for this exact data, but it should not be hard to update it to reflect any changes.
hash2.
map(&:values).
group_by(&:shift).
map do |k, v|
[k, v.flatten.map do |k, v|
[k, hash3.map do |h3|
# lookup a hash from hash1
h1 = hash1.find do |h1|
h3['name'].start_with?(h1['Locator'])
end
# can it be nil btw?
[
h1['name'],
[
h3['name'][/.*(?=-id)/],
h3[k],
h1['Action']
]
]
end.to_h]
end.to_h]
end.to_h
New to Ruby and trying some stuff.
The code below is to convert the array to a string while sorting it and display the sorted results. Where I'm struggling is the use of the capitalize method to caps the all the sorted words.
the_data = ["dog", "cat", "fish", "zebra", "swan", "rabbit", "horse", "albatros", "frog", "mouse", "duck"]
puts "\nThe array:\n"
puts the_data
puts "\n"
puts "\nThe sorted array, capitalized:\n"
to_display = the_data.sort.join(("\n").capitalize)
puts to_display
You can use Array#map to capitalize each word of the Array
to_display = the_data.sort.map(&:capitalize).join("\n")
# => "Albatros\nCat\nDog\nDuck\nFish\nFrog\nHorse\nMouse\nRabbit\nSwan\nZebra"
If you want to capitalize all the letters, you can use upcase
to_display = the_data.sort.map(&:upcase).join("\n")
# => "ALBATROS\nCAT\nDOG\nDUCK\nFISH\nFROG\nHORSE\nMOUSE\nRABBIT\nSWAN\nZEBRA"
Say I have:
a = ["apple", "pear", ["grapes", "berries"], "peach"]
and I want to sort by:
a.sort_by do |f|
f.class == Array ? f.to_s : f
end
I get:
[["grapes", "berries"], "apple", "peach", "pear"]
Where I actually want the items in alphabetical order, with array items being sorted on their first element:
["apple", ["grapes", "berries"], "peach", "pear"]
or, preferably, I want:
["apple", "grapes, berries", "peach", "pear"]
If the example isn't clear enough, I'm looking to sort the items in alphabetical order.
Any suggestions on how to get there?
I've tried a few things so far yet can't seem to get it there. Thanks.
I think this is what you want:
a.sort_by { |f| f.class == Array ? f.first : f }
I would do
a = ["apple", "pear", ["grapes", "berries"], "peach"]
a.map { |e| Array(e).join(", ") }.sort
# => ["apple", "grapes, berries", "peach", "pear"]
Array#sort_by clearly is the right method, but here's a reminder of how Array#sort would be used here:
a.sort do |s1,s2|
t1 = (s1.is_a? Array) ? s1.first : s1
t2 = (s2.is_a? Array) ? s2.first : s2
t1 <=> t2
end.map {|e| (e.is_a? Array) ? e.join(', ') : e }
#=> ["apple", "grapes, berries", "peach", "pear"]
#theTinMan pointed out that sort is quite a bit slower than sort_by here, and gave a reference that explains why. I've been meaning to see how the Benchmark module is used, so took the opportunity to compare the two methods for the problem at hand. I used #Rafa's solution for sort_by and mine for sort.
For testing, I constructed an array of 100 random samples (each with 10,000 random elements to be sorted) in advance, so the benchmarks would not include the time needed to construct the samples (which was not insignificant). 8,000 of the 10,000 elements were random strings of 8 lowercase letters. The other 2,000 elements were 2-tuples of the form [str1, str2], where str1 and str2 were each random strings of 8 lowercase letters. I benchmarked with other parameters, but the bottom-line results did not vary significantly.
require 'benchmark'
# n: total number of items to sort
# m: number of two-tuples [str1, str2] among n items to sort
# n-m: number of strings among n items to sort
# k: length of each string in samples
# s: number of sorts to perform when benchmarking
def make_samples(n, m, k, s)
s.times.with_object([]) { |_, a| a << test_array(n,m,k) }
end
def test_array(n,m,k)
a = ('a'..'z').to_a
r = []
(n-m).times { r << a.sample(k).join }
m.times { r << [a.sample(k).join, a.sample(k).join] }
r.shuffle!
end
# Here's what the samples look like:
make_samples(6,2,4,4)
#=> [["bloj", "izlh", "tebz", ["lfzx", "rxko"], ["ljnv", "tpze"], "ryel"],
# ["jyoh", "ixmt", "opnv", "qdtk", ["jsve", "itjw"], ["pnog", "fkdr"]],
# ["sxme", ["emqo", "cawq"], "kbsl", "xgwk", "kanj", ["cylb", "kgpx"]],
# [["rdah", "ohgq"], "bnup", ["ytlr", "czmo"], "yxqa", "yrmh", "mzin"]]
n = 10000 # total number of items to sort
m = 2000 # number of two-tuples [str1, str2] (n-m strings)
k = 8 # length of each string
s = 100 # number of sorts to perform
samples = make_samples(n,m,k,s)
Benchmark.bm('sort_by'.size) do |bm|
bm.report 'sort_by' do
samples.each do |s|
s.sort_by { |f| f.class == Array ? f.first : f }
end
end
bm.report 'sort' do
samples.each do |s|
s.sort do |s1,s2|
t1 = (s1.is_a? Array) ? s1.first : s1
t2 = (s2.is_a? Array) ? s2.first : s2
t1 <=> t2
end
end
end
end
user system total real
sort_by 1.360000 0.000000 1.360000 ( 1.364781)
sort 4.050000 0.010000 4.060000 ( 4.057673)
Though it was never in doubt, #theTinMan was right! I did a few other runs with different parameters, but sort_by consistently thumped sort by similar performance ratios.
Note the "system" time is zero for sort_by. In other runs it was sometimes zero for sort. The values were always zero or 0.010000, leading me to wonder what's going on there. (I ran these on a Mac.)
For readers unfamiliar with Benchmark, Benchmark#bm takes an argument that equals the amount of left-padding desired for the header row (user system...). bm.report takes a row label as an argument.
You are really close. Just switch .to_s to .first.
irb(main):005:0> b = ["grapes", "berries"]
=> ["grapes", "berries"]
irb(main):006:0> b.to_s
=> "[\"grapes\", \"berries\"]"
irb(main):007:0> b.first
=> "grapes"
Here is one that works:
a.sort_by do |f|
f.class == Array ? f.first : f
end
Yields:
["apple", ["grapes", "berries"], "peach", "pear"]
a.map { |b| b.is_a?(Array) ? b.join(', ') : b }.sort
# => ["apple", "grapes, berries", "peach", "pear"]
Replace to_s with join.
a.sort_by do |f|
f.class == Array ? f.join : f
end
# => ["apple", ["grapes", "berries"], "peach", "pear"]
Or more concisely:
a.sort_by {|x| [*x].join }
# => ["apple", ["grapes", "berries"], "peach", "pear"]
The problem with to_s is that it converts your Array to a string that starts with "[":
"[\"grapes\", \"berries\"]"
which comes alphabetically before the rest of your strings.
join actually creates the string that you had expected to sort by:
"grapesberries"
which is alphabetized correctly, according to your logic.
If you don't want the arrays to remain arrays, then it's a slightly different operation, but you will still use join.
a.map {|x| [*x].join(", ") }.sort
# => ["apple", "grapes, berries", "peach", "pear"]
Sort a Flattened Array
If you just want all elements of your nested array flattened and then sorted in alphabetical order, all you need to do is flatten and sort. For example:
["apple", "pear", ["grapes", "berries"], "peach"].flatten.sort
#=> ["apple", "berries", "grapes", "peach", "pear"]
I have a hash returned to me in ruby
test_string = "{cat=6,bear=2,mouse=1,tiger=4}"
I need to get a list of these items in this form ordered by the number.
animals = [cat, tiger, bear, mouse]
My thoughts were to_s this in ruby and split on the '=' character. Then try to order them and put in a new list. Is there an easy way to do this in ruby? Sample code would be greatly appreciated.
s = "{cat=6,bear=2,mouse=1,tiger=4}"
a = s.scan(/(\w+)=(\d+)/)
p a.sort_by { |x| x[1].to_i }.reverse.map(&:first)
a = test_string.split('{')[1].split('}').first.split(',')
# => ["cat=6", "bear=2", "mouse=1", "tiger=4"]
a.map{|s| s.split('=')}.sort_by{|p| p[1].to_i}.reverse.map(&:first)
# => ["cat", "tiger", "bear", "mouse"]
Not the most elegant way to do it, but it works:
test_string.gsub(/[{}]/, "").split(",").map {|x| x.split("=")}.sort_by {|x| x[1].to_i}.reverse.map {|x| x[0].strip}
The below code should do it.
Explained the steps inline
test_string.gsub!(/{|}/, "") # Remove the curly braces
array = test_string.split(",") # Split on comma
array1= []
array.each {|word|
array1<<word.split("=") # Create an array of arrays
}
h1 = Hash[*array1.flatten] # Convert Array into Hash
puts h1.keys.sort {|a, b| h1[b] <=> h1[a]} # Print keys of the hash based on sorted values
test_string = "{cat=6,bear=2,mouse=1,tiger=4}"
Hash[*test_string.scan(/\w+/)].sort_by{|k,v| v.to_i }.map(&:first).reverse
#=> ["cat", "tiger", "bear", "mouse"]
I want to sort an array in particular order given in another array.
EX: consider an array
a=["one", "two", "three"]
b=["two", "one", "three"]
Now I want to sort array 'a' in the order of 'b', i.e
a.each do |t|
# It should be in the order of 'b'
puts t
end
So the output should be
two
one
three
Any suggestions?
Array#sort_by is what you're after.
a.sort_by do |element|
b.index(element)
end
More scalable version in response to comment:
a=["one", "two", "three"]
b=["two", "one", "three"]
lookup = {}
b.each_with_index do |item, index|
lookup[item] = index
end
a.sort_by do |item|
lookup.fetch(item)
end
If b includes all elements of a and if elements are unique, then:
puts b & a
Assuming a is to be sorted with respect to order of elements in b
sorted_a =
a.sort do |e1, e2|
b.index(e1) <=> b.index(e2)
end
I normally use this to sort error messages in ActiveRecord in the order of appearance of fields on the form.