chunk.rb

describe '#chunk' do
  def chunk(arr)
    arr.inject([]) do |chunks, elem|
      current_sequence = chunks.last || []
      if elem == current_sequence.last
        current_sequence << elem
      else
        chunks << [elem]
      end
      chunks
    end
  end

  it 'chunks an array of equal elements into an array of one array' do
    chunk([1,1]).should == [ [1,1] ]
  end

  it 'chunks an array of different elements into different arrays' do
    chunk([1,2]).should == [ [1], [2] ]
  end

  it 'chunks an array with contiguous sets of elements into an array of arrays of those sets' do
    chunk([1,1,1,2,2,1,1,2,2,2]).should == [ [1,1,1], [2,2], [1,1] , [2,2,2] ]
  end

  it 'chunks an array with an odd number of elements properly' do
    chunk([1,1,1,2,2,1,1,2,2]).should == [ [1,1,1], [2,2], [1,1] , [2,2] ]
  end
end

def chunk(arr)
  arr.inject([]) do |acc, elem|
    current_sequence = acc.last || []
    (elem == current_sequence.last) ? current_sequence << elem : acc << [elem]
    acc
  end
end

Similar idea:

def chunk(arr)
  arr.inject([]) {|on_boundary_array,x|
    if on_boundary_array == [] || on_boundary_array[-1][0] != x
      on_boundary_array << [x]
    else
      on_boundary_array[-1] << x
    end
    on_boundary_array
  }
end

I've updated with specs, using Thuva's so far with some minor changes for readability

For posterity reasons, I am including our original solution here:

def chunk(arr)
  chunks = []
  group_chunks(arr) do |group|
    chunks << group
  end
  chunks
end 

def group_chunks(arr)
  group = []
  arr.each_cons(2) do |record, next_record|
    group << record
    if next_record.nil? || record != next_record
      yield(group)
      group = []
    end 
  end
end

this is my solution:

describe '#chunk' do
  def chunk(arr)
    c = arr.cycle
    c.next
    counter = 0

    arr.inject([[]]) do |results, element|
      counter += 1
      results.last << element

      if (element != c.next && counter < arr.length)
        results << []   
      end

      results
    end  

  end

  it 'chunks an array of equal elements into an array of one array' do
    chunk([1,1]).should == [ [1,1] ]
  end

  it 'chunks an array of different elements into different arrays' do
    chunk([1,2]).should == [ [1], [2] ]
  end

  it 'chunks an array with contiguous sets of elements into an array of arrays of those sets' do
    chunk([1,1,1,2,2,1,1,2,2,2]).should == [ [1,1,1], [2,2], [1,1] , [2,2,2] ]
  end

  it 'chunks an array with an odd number of elements properly' do
    chunk([1,1,1,2,2,1,1,2,2]).should == [ [1,1,1], [2,2], [1,1] , [2,2] ]
  end
end

def chunk(arr):
    c = [[arr[0]]] if arr else [[]]
    for x in arr[1:]:
        if x in c[-1]: c[-1].append(x)
        else: c.append([x])
    return c

Totally obfuscated one-liner:

def chunk(arr)
  arr.inject([[arr.shift]]) { |c, v| c.last.include?(v) ? c.last << v : c << [v]; c }
end

Jonathan, I can't let you beat me (this is not FIFA). Here's my one-liner and it handles the case where the input is an empty array :-)

def chunk(arr)
  arr.inject([]) {|c, v| (v == (c.last || []).last) ? (c.last || []) << v : c << [v]; c}
end

Congrats, you have won the trophy. Now, you just to get better in FIFA, -D... Leandro.

On 11-09-01 2:57 PM, "thuva" ***@***.*** wrote: Jonathan, I can't let you beat me (this is not FIFA). Here's my one-liner and it handles the case where the input is an empty array :-) ``` ruby def chunk(arr) arr.inject([]) {|c, v| (v == (c.last || []).last) ? (c.last || []) << v : c << [v]; c} end ```

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