ruby,algorithm,search,recursion , Recursive solution doesn't iterate correctly

## Question:

Tag: ruby,algorithm,search,recursion

I'm working through a toy problem in Ruby: how to produce all possible 10-digit phone numbers where each successive number is adjacent to the last on the keypad. I've represented the adjacent relationships between numbers, and have a recursive function, but my method isn't iterating through the whole solution space. It's just finding the first solution and returning.

Here's my code:

adjacencies = { 1 => [2, 4],
2 => [1, 3, 5],
3 => [2, 6],
4 => [1, 5, 7],
5 => [2, 4, 6, 8],
6 => [3, 5, 9],
7 => [4, 8],
8 => [5, 7, 9, 0],
9 => [6, 8],
0 => [8]
}

phone_length = 10
partial_phone_number = partial_phone_number + to_append.to_s
if (partial_phone_number.length == phone_length)
return partial_phone_number
else
end
end
end

(0..9).each do |n|
end


And here is the output when I run it:

0852121212
1212121212
2121212121
3212121212
4121212121
5212121212
6321212121
7412121212
8521212121
9632121212


The first time you enter the adjacencies[to_append].each, you immediately return from the method, therefore the loop will never be executed more than once.

You need to

1. return a list of phone numbers instead of just a single phone number
2. build that list somehow in your recursive call

# Related:

## is there an equivalent of the ruby any method in javascript?

javascript,arrays,ruby,iteration
Is there an equivalent of ruby's any method for arrays but in javascript? I'm looking for something like this: arr = ['foo','bar','fizz', 'buzz'] arr.any? { |w| w.include? 'z' } #=> true I can get a similar effect with javascript's forEach method but it requires iterating through the entire array rather...

## On rendering from controller, current_page method does not seem to work

ruby-on-rails,ruby,ruby-on-rails-4,model-view-controller
I have a navigation bar included in application.html.erb. Because for some pages, such as the signup page, I need to place additional code inside the navigation bar, I have excluded those pages for showing the navigation bar through application.html.erb and instead included it in their respective view pages. See code...

## Understanding Big-Ω (Big-Omega) notation

algorithm,big-o
I was doing some reading on logarithms and the rate of growth of the running time of algorithms. I have, however, a problem understanding the Big-Ω (Big-Omega) notation. I know that we use it for 'asymptotic lower bounds', and that we can express the idea that an algorithm takes at...

## Ruby- get a xml node value

ruby,xml
can someone help me in extracting the node value for the element "Name". Type 1: I am able to extract the "name" value for the below xml by using the below code <Element> <Details> <ID>20367</ID> <Name>Ram</Name> <Name>Sam</Name> </Details> </Element> doc = Nokogiri::XML(response.body) values = doc.xpath('//Name').map{ |node| node.text}.join ',' puts values...

## What is this algorithm mapping coordinates to numbers called?

algorithm,coordinates,coordinate-systems,coordinate
I'm writing a program for visualizing crystals. As a part of the program, I have to generate all different basic points in a lattice structure. For those that aren't familiar with crystallography, you can find the most general cases of these structures here: https://en.wikipedia.org/wiki/Hermann%E2%80%93Mauguin_notation#Lattice_types The problem was that I wanted...

## Appending an element to a page in VoltRb

html,ruby,opalrb,voltrb

## Rails shared controller actions

ruby-on-rails,ruby,ruby-on-rails-4
I am having trouble building a controller concern. I would like the concern to extend the classes available actions. Given I have the controller 'SamplesController' class SamplesController < ApplicationController include Searchable perform_search_on(Sample, handle: [ClothingType, Company, Collection, Color]) end I include the module 'Searchable' module Searchable extend ActiveSupport::Concern module ClassMethods def...

## Get X days out of an Array

ruby,ruby-on-rails-4
I have an array filled with Datetime objects: [Mon, 22 Jun 2015, Tue, 23 Jun 2015, Wed, 24 Jun 2015, Thu, 25 Jun 2015, Fri, 26 Jun 2015, Sat, 27 Jun 2015, Sun, 28 Jun 2015] I know how to select what I want from the array ex: week.select{|x|x.monday? ||...

## Using Ruby Pathname to access relative directory

ruby,path,pathname
Given I have a relative path pointing to a directory how can I use it with Ruby's Pathname or File library to get the directory itself? p = Pathname.new('dir/') p.dirname => . p.directory? => false I have tried './dir/', 'dir/', 'dir'. What I want is p.dirname to return 'dir'. I...

## How to pivot array into another array in Ruby

arrays,ruby,csv
I have a multidimensional array like this one : myArray = [["Alaska","Rain","3"],["Alaska","Snow","4"],["Alabama","Snow","2"],["Alabama","Hail","1"]] I would like to end up with CSV output like this. State,Snow,Rain,Hail Alaska,4,3,nil Alabama,2,nil,1 I know that to get this outputted to CSV the way I want it I have to have output array like this: outputArray =[["State","Snow","Rain","Hail"],["Alaska",4,3,nil],["Alabama",2,nil,1]]...

## Seeding fails validation for nested tables (validates_presence_of)

ruby-on-rails,ruby,validation,ruby-on-rails-4,associations
An Organization model has a 1:many association with a User model. I have the following validation in my User model file: belongs_to :organization validates_presence_of :organization_id, :unless => 'usertype==1' If usertype is 1, it means the user will have no organization associated to it. For a different usertype the presence of...

## Loop until i get correct user

ruby,redis
I have users stored in Redis and want to be able to call only certain subsets from a set, if i don't get the correct user back i want to put it back in the set and then try again until i get one of the desired users @redis =...

## How could I padding spaces to a fix length

ruby
I need all strings' length with 5 Original [477, 4770,] Expected ["477 ", "4770 "] How could I do it with Ruby ?...

## Does there exist an algorithm for iterating through all strings that conform to a particular regex?

c#,regex,algorithm
I'm making a script to try and hack into an account whose login password is at least 8 characters long and includes at least 1 number, 1 special character and 1 capital letter. I will use brute force. Is there a compact, elegant and efficient way to iterate through every...

## Dynamic programming: how to design algorithm for when there are two factors to consider?

algorithm,optimization,dynamic-programming,frequency
I have the following problem and I only have a slight idea about it: Consider a tape storage problem. Given n files of length l1,...,ln and frequencies with which they are accessed f1,...,fn, where sum of all frequencies is 1 and 0<fi<1. "Optimal" means to minimize the average retrieval time...

## Identify that a string could be a datetime object

python,regex,algorithm,python-2.7,datetime
If I knew the format in which a string represents date-time information, then I can easily use datetime.datetime.strptime(s, fmt). However, without knowing the format of the string beforehand, would it be possible to determine whether a given string contains something that could be parsed as a datetime object with the...

## Can't map a range of dates in Ruby/Rails

ruby-on-rails,ruby
I'm trying to map a range of dates and pass them to my view as an array, as follows: from, to = Date.parse("2014-01-01"), Date.yesterday date_range = (from..to) @mapped_dates = date_range.map {|date| date.strftime("%b %e")} I reference them in some JS in my view as follows: dateLabels = <%= raw @mapped_dates.to_json %>;...

## Disconnect all vertices in a graph - Algorithm

algorithm,graph
I am looking for an algorithm that finds minimal subset of vertices such that by removing this subset (and edges connecting these vertices) from graph all other vertices become unconnected (i.e. the graph won't have any edges). Is there such algorithm? If not: Could you recommend some kind of heuristics...

## 3 X 3 magic square recursively

c++,algorithm,math,recursion
I'm trying to find all possible solutions to the 3X3 magic square. There should be exactly 8 solutions. My code gets them all but there are a lot of repeats. I'm having a hard time tracking the recursive steps to see why I'm getting all the repeats. // This program...

## Rails Association Guidance [on hold]

ruby-on-rails,ruby,ruby-on-rails-4,ruby-on-rails-3.2
I am new to rails 4. I have gone through lots of tutorials and trying to solve below scenario. But still no success. Can anybody point me in the right direction. How to handle associations for below scenario. Scenario: 1. Patient can have many surgeries. 2. Surgery has two types...

## Ruby: How to copy the multidimensional array in new array?

ruby-on-rails,arrays,ruby,multidimensional-array
seating_arrangement [ [:first, :second, :none], [:first, :none, :second], [:second, :second, :first], ] I need to copy this array into new array. I tried to do it by following code: class Simulator @@current_state def initialize(seating_arrangement) @@current_state = seating_arrangement.dup end But whenever I am making any changes to seating_arrangement current_state changes automatically....

## Heroku rake db:migrate failing - uninitialized constant

ruby-on-rails,ruby,heroku
My app is working fine locally and my push to Heroku was successful. But, when I run heroku run rake db:migrate, I get the following error: NameError: uninitialized constant AddWeightToExercises Here is the failed migration: class AddWeightToExercise < ActiveRecord::Migration def change add_column :exercises, :weight, :float end end edit: Thanks for...

ruby-on-rails,ruby,rest,activerecord,one-to-many
I'm creating a rails application that is a backend for a mobile application. The backend is implemented with a RESTful web API. Currently I am trying to add gamification to the platform through the use of badges that can be earned by the user. Right now the badges are tied...

## Ruby access words in string

ruby
I don't understand the best method to access a certain word by it's number in a string. I tried using [] to access a word but instead it returns letter. puts s # => I went for a walk puts s[3] # => w ...

## How to get return value from a forked / spawned process in Ruby?

ruby,process,output,fork,spawn
My simple test program: pid = Process.spawn("sleep 10;date") How can I place the output (eg stdout) of the "date" command in a variable when it is available? I don't want to use a file for the data exchange....

## Make instance variable accessible through hash in Ruby

ruby-on-rails,ruby,ruby-on-rails-4,activerecord
In Rails, ActiveRecord objects, attributes are accessible via method as well as through Hash. Example: user = User.first # Assuming User to be inheriting from ActiveRecord::Base user.name # Accessing attribute 'name' via method user[:name] # Attribute 'name' is accessible via hash as well How to make instance variables accessible through...