assignment (kind of) complete

.rspec

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+--color
+--require spec_helper

Gemfile

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+source "https://rubygems.org"
+
+gem "rspec"
+gem 'guard-rspec', require: false

Gemfile.lock

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+GEM
+  remote: https://rubygems.org/
+  specs:
+    coderay (1.1.1)
+    diff-lcs (1.3)
+    ffi (1.9.18)
+    formatador (0.2.5)
+    guard (2.14.1)
+      formatador (>= 0.2.4)
+      listen (>= 2.7, < 4.0)
+      lumberjack (~> 1.0)
+      nenv (~> 0.1)
+      notiffany (~> 0.0)
+      pry (>= 0.9.12)
+      shellany (~> 0.0)
+      thor (>= 0.18.1)
+    guard-compat (1.2.1)
+    guard-rspec (4.7.3)
+      guard (~> 2.1)
+      guard-compat (~> 1.1)
+      rspec (>= 2.99.0, < 4.0)
+    listen (3.1.5)
+      rb-fsevent (~> 0.9, >= 0.9.4)
+      rb-inotify (~> 0.9, >= 0.9.7)
+      ruby_dep (~> 1.2)
+    lumberjack (1.0.11)
+    method_source (0.8.2)
+    nenv (0.3.0)
+    notiffany (0.1.1)
+      nenv (~> 0.1)
+      shellany (~> 0.0)
+    pry (0.10.4)
+      coderay (~> 1.1.0)
+      method_source (~> 0.8.1)
+      slop (~> 3.4)
+    rb-fsevent (0.9.8)
+    rb-inotify (0.9.8)
+      ffi (>= 0.5.0)
+    rspec (3.5.0)
+      rspec-core (~> 3.5.0)
+      rspec-expectations (~> 3.5.0)
+      rspec-mocks (~> 3.5.0)
+    rspec-core (3.5.4)
+      rspec-support (~> 3.5.0)
+    rspec-expectations (3.5.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.5.0)
+    rspec-mocks (3.5.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.5.0)
+    rspec-support (3.5.0)
+    ruby_dep (1.5.0)
+    shellany (0.0.1)
+    slop (3.6.0)
+    thor (0.19.4)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  guard-rspec
+  rspec
+
+BUNDLED WITH
+   1.14.4

Guardfile

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+# A sample Guardfile
+# More info at https://github.com/guard/guard#readme
+
+## Uncomment and set this to only include directories you want to watch
+# directories %w(app lib config test spec features) \
+#  .select{|d| Dir.exists?(d) ? d : UI.warning("Directory #{d} does not exist")}
+
+## Note: if you are using the `directories` clause above and you are not
+## watching the project directory ('.'), then you will want to move
+## the Guardfile to a watched dir and symlink it back, e.g.
+#
+#  $ mkdir config
+#  $ mv Guardfile config/
+#  $ ln -s config/Guardfile .
+#
+# and, you'll have to watch "config/Guardfile" instead of "Guardfile"
+
+# Note: The cmd option is now required due to the increasing number of ways
+#       rspec may be run, below are examples of the most common uses.
+#  * bundler: 'bundle exec rspec'
+#  * bundler binstubs: 'bin/rspec'
+#  * spring: 'bin/rspec' (This will use spring if running and you have
+#                          installed the spring binstubs per the docs)
+#  * zeus: 'zeus rspec' (requires the server to be started separately)
+#  * 'just' rspec: 'rspec'
+
+guard :rspec, cmd: "bundle exec rspec" do
+  require "guard/rspec/dsl"
+  dsl = Guard::RSpec::Dsl.new(self)
+
+  # Feel free to open issues for suggestions and improvements
+
+  # RSpec files
+  rspec = dsl.rspec
+  watch(rspec.spec_helper) { rspec.spec_dir }
+  watch(rspec.spec_support) { rspec.spec_dir }
+  watch(rspec.spec_files)
+
+  # Ruby files
+  ruby = dsl.ruby
+  dsl.watch_spec_files_for(ruby.lib_files)
+
+  # Rails files
+  rails = dsl.rails(view_extensions: %w(erb haml slim))
+  dsl.watch_spec_files_for(rails.app_files)
+  dsl.watch_spec_files_for(rails.views)
+
+  watch(rails.controllers) do |m|
+    [
+      rspec.spec.call("routing/#{m[1]}_routing"),
+      rspec.spec.call("controllers/#{m[1]}_controller"),
+      rspec.spec.call("acceptance/#{m[1]}")
+    ]
+  end
+
+  # Rails config changes
+  watch(rails.spec_helper)     { rspec.spec_dir }
+  watch(rails.routes)          { "#{rspec.spec_dir}/routing" }
+  watch(rails.app_controller)  { "#{rspec.spec_dir}/controllers" }
+
+  # Capybara features specs
+  watch(rails.view_dirs)     { |m| rspec.spec.call("features/#{m[1]}") }
+  watch(rails.layouts)       { |m| rspec.spec.call("features/#{m[1]}") }
+
+  # Turnip features and steps
+  watch(%r{^spec/acceptance/(.+)\.feature$})
+  watch(%r{^spec/acceptance/steps/(.+)_steps\.rb$}) do |m|
+    Dir[File.join("**/#{m[1]}.feature")][0] || "spec/acceptance"
+  end
+end

README.md

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 # assignment_search
+
+## Efraim
+
 Marco?  Polo!
 
 [A data structures and algorithms Ruby challenge from the Viking Code School](http://www.vikingcodeschool.com)
+
+## Warmup 1: BFS and DFS Concepts
+
+1. What data structure is used to implement DFS?
+
+A Tree and a Graph, but the concept can be applied to any sequence that can be traversed.
+
+2. What data structure is typically used to implement BFS?
+
+Same as before.
+
+3. Which one can be done recursively? (the clue should be the data structure)
+
+The Tree.
+
+4. Which one would you use to print a list of all the nodes in a tree or graph, starting with depth 1, then depth 2, then depth 3 etc.?
+
+Any one of the two, but since I like recursion I'd use a Tree.
+
+5. What is the difference between a tree and a graph?
+
+The Tree is a data structure represented by nodes; these nodes may have parent and child nodes.
+
+The Graph may be represented as nodes too, but they don't have a hierarchy between each other.
+
+## Pseudocode
+
+1. Searching a simple tree of nodes where each Node has an array of child nodes (some_node.children) using DFS.
+
+```ruby
+def depth_first_search(arr, obj)
+  return if arr.nil?
+  if arr.is_a? Array
+    depth_first_search(arr[0], obj) || depth_first_search(arr[1..-1], obj)
+  else
+    arr if arr == obj
+  end
+end
+```
+
+2. Searching the same tree using BFS.
+
+```ruby
+def breadth_first_search(queue, obj)
+  if queue.empty?
+    nil
+  else
+    first, rest = queue[0], queue[1..-1]
+    if first.is_a? Array
+      rest.push(first[0])
+      rest.push(first[1..-1])
+      breadth_first_search(rest, obj)
+    else
+      return first if first == obj
+      breadth_first_search(rest, obj)
+    end
+  end
+end
+```
+
+3. Searching a graph (represented however you feel most comfortable -- Edge List, Adjacency List or Adjacency Matrix) using DFS.
+
+Same concept as the upper code.
+
+4. Searching the same graph using BFS.
+
+Same concept as the upper code.

lib/knight.rb

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+# find the exact sequence of moves required to get from any given
+# square to another square on the board
+# 8x8
+
+Move = Struct.new("Move", :x, :y, :depth, :children, :parent)
+
+# Set up a very basic MoveTree class (as in, "a tree of moves").
+# It should construct a tree of potential moves from a given position by using
+# a series of Move structs.
+# It should take two inputs -- a coordinate pair to represent the starting
+# position and a max_depth value which prevents the tree from
+# continuing infinitely large [ok]
+
+class MoveTree
+  attr_accessor :axis, :max_depth, :root
+
+  def initialize(axis, max_depth)
+    @axis = axis
+    @max_depth = max_depth
+    @root = MoveTree.build_tree!(Move.new(axis[0], axis[1], 0), 0, max_depth)
+  end
+
+  # ---------------------------------------------------------------
+  # Access
+  # ---------------------------------------------------------------
+
+  def children
+    root.children
+  end
+
+  def x
+    root.x
+  end
+
+  def y
+    root.y
+  end
+
+  # ---------------------------------------------------------------
+  # Class Methods
+  # ---------------------------------------------------------------
+
+  def self.knight_moves
+    [
+      [2, 1], [2, -1], [-2, 1], [-2, -1],
+      [1, 2], [-1, 2], [1, -2], [-1, -2]
+    ]
+  end
+
+  def self.moves_for(parent, depth)
+    MoveTree.knight_moves.map do |move|
+      to_x, to_y = move
+      Move.new(parent.x - to_x, parent.y - to_y, depth, nil, parent)
+    end.select do |move|
+      MoveTree.within_board_limits?(move.x, move.y)
+    end
+  end
+
+  def self.build_tree!(parent, depth, max_depth)
+    return parent if depth == max_depth
+    if parent.children.nil?
+      depth += 1
+      parent.children = MoveTree.moves_for(parent, depth)
+      MoveTree.build_tree!(parent, depth, max_depth)
+    else
+      parent.children.each do |node|
+        MoveTree.build_tree!(node, depth, max_depth)
+      end
+      parent
+    end
+  end
+
+  def self.within_board_limits?(x, y)
+    x >= 0 && x <= 7 &&
+    y >= 0 && y <= 7
+  end
+
+  def self.length(tr)
+    if tr.children
+      tr.children.length + tr.children.map{ |c| MoveTree.length(c) }.sum
+    else
+      0
+    end
+  end
+
+  # ---------------------------------------------------------------
+  # Instance Methods
+  # ---------------------------------------------------------------
+
+  def length
+    MoveTree.length(root) + 1
+  end
+
+  def depth
+    d = 0
+    parent = root
+    while true
+      break if parent.children.nil?
+      d += 1
+      parent = parent.children[0]
+    end
+    d
+  end
+
+  def inspect
+    "Your tree has #{length} Move nodes and a maximum depth of #{depth}"
+  end
+
+end