I am relatively new to coding and am learning ruby right now. I came across a problem where I have a huge data record (>100k record) consisting of unique ID and another consisting of the date of birth. So it's basically a 2D array. How do I go about creating a method such that every time when I key in method(year), it will give me all the unique ID of those born in the year i choose? And how do I loop this?
The method I tried doing is as follow:
def Id_with_year(year)
emPloyee_ID_for_searching_year = [ ]
employeelist.sort_by!{|a,b|b}
if employeelist.select{|a,b| b == year}.map{|a,b| a}
return emPloyee_ID_for_searching_year
end
end
I should point out that the ID are sorted. That's why I am trying to sort the year in this method so that it will give me all the ID for the year I key in. The output I had was that it returned me [ ] with nothing inside instead of the ID.
Sidenote: methods in ruby are to be named in snake case (this is not mandatory, though.)
The problem you experience is you return what was never changed. The below should work:
def id_with_year(year)
employeelist.sort_by(&:last) # sorting by last element of array
.select{|_,b| b == year} # select
.map(&:first) # map to the first element
end
Related
Currently trying to generate a random number in a specific range;
and ensure that it would be unique against others stored records.
Using Mysql. Could be like an id, incremented; but can't be it.
Currently testing other existing records in an 'expensive' manner;
but I'm pretty sure that there would be a clean 1/2 lines of code to use
Currently using :
test = 0
Order.all.each do |ord|
test = (0..899999).to_a.sample.to_s.rjust(6, '0')
if Order.find_by_number(test).nil? then
break
end
end
return test
Thanks for any help
Here your are my one-line solution. It is also the quicker one since calls .pluck to retrieve the numbers from the Order table. .select instantiates an "Order" object for every record (that is very costly and unnecessary) while .pluck does not. It also avoids to iterate again each object with a .map to get the "number" field. We can avoid the second .map as well if we convert, using CAST in this case, to a numeric value from the database.
(Array(0...899999) - Order.pluck("CAST('number' AS UNSIGNED)")).sample.to_s.rjust(6, '0')
I would do something like this:
# gets all existing IDs
existing_ids = Order.all.select(:number).map(&:number).map(&:to_i)
# removes them from the acceptable range
available_numbers = (0..899999).to_a - existing_ids
# choose one (which is not in the DB)
available_numbers.sample.to_s.rjust(6, '0')
I think, you can do something like below :
def uniq_num_add(arr)
loop do
rndm = rand(1..15) # I took this range as an example
# random number will be added to the array, when the number will
# not be present
break arr<< "%02d" % rndm unless arr.include?(rndm)
end
end
array = []
3.times do
uniq_num_add(array)
end
array # => ["02", "15", "04"]
I'm trying to use the two following methods to recursively traverse arrays of arrays until the bottom and then come back up with the match results.
You know how in a tennis tournament they start with 32 matches and pair by pair the winner moves ahead, and at the end there's only one winner? That's what I want to replicate in Ruby.
I created a match_winner that always returns the first array for the sake of simplicity. Then, I send the whole tournament array into winner that calls itself recursively until it finds a simple array corresponding to a single match.
def match_winner(array_of_arrays)
return array_of_arrays[0]
end
def winner(tournament)
if tournament[0][0].is_a?(String)
return match_winner(tournament)
else
tournament.each{|e|
winner(e)
}
end
end
tournament = [
[["one", "two"],["three", "four"]],
[["five", "six"],["seven", "eight"]]
]
puts winner(tournament).inspect
Which outputs:
[[["one", "two"], ["three", "four"]], [["five", "six"], ["seven", "eight"]]]
I tried different permutations and variations on this algorithm but I couldn't make it work correctly and return only the final winner.
Does anyone see anything obviously wrong here?
Now I'm calling winner.
I know that the question looks like it's answered, but I just did the same problem and I have to say that simply changing each to map didn't work for me, because, as the code posted, the result is an array of the first-round winners. What worked for me is:
def winner(tournament)
if tournament[0][0].is_a?(String)
return match_winner(tournament)
else
tournament.map!{|e| #use map!, because we need to apply winner() to new values
e=winner(e) #assign new value somewhere, so recursion can climb back
}
end
end
Maybe more experienced developers can explain why that is. Without these two tips it won't work.
And yes, I know "bang" is a bad coding style, danger danger high voltage, but it's my second day with Ruby and I wanted to get this to work.
And, to understand recursion, you have to understand recursion.
Looks like you want map, not each, and, as a commenter above notes, you didn't call winner in the above code.
When you call:
tournament.each {...}
that method actually returns the tournament, which is thus what winner returns.
What you want is to replace it with
tournament.map {...}
which returns a new array consisting of calling "winner" on each element of tournament.
Assuming you have 2^n number of games always and match_winner works ok:
def winner(game)
if game[0][0][0] == game[0][0][0][0]
match_winner( [ game[0], game[1] ] )
else
match_winner( [winner(game[0]), winner(game[1])] )
end
end
I have two arrays and I want to see the total number of matches, between the arrays individual items that their are.
For example arrays with:
1 -- House, Dog, Cat, Car
2 -- Cat, Book, Box, Car
Would return 2.
Any ideas? Thanks!
EDIT/
Basically I have two forms (for two different types of users) that uses nested attributes to store the number of skills they have. I can print out the skills via
current_user.skills.each do |skill| skill.name
other_user.skills.each do |skill| skill.name
When I print out the array, I get: #<Skill:0x1037e4948>#<Skill:0x1037e2800>#<Skill:0x1037e21e8>#<Skill:0x1037e1090>#<Skill:0x1037e0848>
So, yes, I want to compare the two users skills and return the number that match. Thanks for your help.
This works:
a = %w{house dog cat car}
b = %w{cat book box car}
(a & b).size
Documentation: http://www.ruby-doc.org/core/classes/Array.html#M000274
To convert classes to an array using the name, try something like:
class X
def name
"name"
end
end
a = [X.new]
b = [X.new]
(a.map{|x| x.name} & b.map{|x| x.name}).size
In your example, a is current_user.skills and b is other_users.skills. x is simply a reference to the current index of the array as the map action loops through the array. The action is documented in the link I provided.
I'm trying to build a hash from an array. Basically I want to take the unique string values of the array and build a hash with a key. I'm also trying to figure out how to record how many times that unique word happens.
#The text from the .txt file:
# **Bob and George are great! George and Sam are great.
#Bob, George, and sam are great!**
#The source code:
count_my_rows = File.readlines("bob.txt")
row_text = count_my_rows.join
puts row_text.split.uniq #testing to make sure array is getting filled
Anyways I've tried http://ruby-doc.org/core/classes/Hash.html
I think I need to declare a empty hash with name.new to start I have no idea how to fill it up though. I'm assuming some iteration through the array fills the hash. I'm starting to think I need to record the value as a separate array storing the time it occurs and the word then assign the hash key to it.
Example = { ["Bob",2] => 1 , ["George",3], =>2 }
Leave some code so I can mull over it.
To get you started,
h={}
h.default=0
File.read("myfile").split.each do |x|
h[x]+=1
end
p h
Note: this is not complete solution
This is what I have so far
ages = [20,19,21,17,31,33,34]
names = [Bob, Bill, Jill, Aimee, Joe, Matt, Chris]
How do I take ages and apply a method to it to extract the largest integer out of it and learn its indexed position. The reason being I want to know which person in names is the oldest. Parallel assignment is blocking my ability to do a .sort on the array becasue it changes the position of element associted with names.
Please include code to mull over thanks,
ages.zip(names).max
names[ages.index(ages.max)]
What it does is find the maximum value in ages (ages.max), get the index of the first matching value in ages, and use it to get the corresponding person. Note that if two or more people have the same age which is the maximum, it'll only give you the name of the first one in the array.
Edit: To address your comment, I'm not sure why you need this parallel arrays structure (it'd be much easier if you just had a person object). Nevertheless, you can try something like:
indices = []
ages.each_with_index { |age, i| indices << i if age < 20 }
indices.each { |i| puts names[i] }