merge_sorted.rb

class Array
  def merge_sorted(other)
    i = 0
    j = 0
    sorted = []
    while(i < self.length || j < other.length) do
      l = self[i]
      m = other[j]
      if l.nil? || l >= m
        sorted << m
        j += 1
      elsif m.nil? || l < m
        sorted << l
        i += 1
      end
    end

    sorted
  end
end

require 'rspec'

describe "#merge_sorted" do
  it "merges to sorted equal length arrays" do
    expect([1,3,5].merge_sorted([2,4,6])).to eq([1,2,3,4,5,6])
  end

  it "merges to uneven length arrays" do
    expect([1].merge_sorted([2,4,6])).to eq([1,2,4,6])
  end

  it "handles empty arrays" do
    expect([].merge_sorted([2,4,6])).to eq([2,4,6])
  end
end