complementary pairs of array items

gistfile1.rb

def dups(arr, i, j)
  l_dups, r_dups = 0, 0
  i.upto(j) do |n|
    break if arr[n] != arr[i]
    l_dups +=1
  end
  j.downto(i) do |n|
    break if arr[n] != arr[j]
    r_dups += 1
  end
  [l_dups, r_dups]
end

def complementary_pairs(k, arr)
  arr.sort!
  p arr
  i, j, count = 0, arr.size-1, 0

  while i <= j
    if arr[i] + arr[j] == k
      # finish - center of an array
      if arr[i] == arr[j]
        count += (1+j-i)**2
        break
      else
        # duplicate pairs - for [i,-,...,-,j]
        if i+2 < j and arr[i+1] == arr[i] and arr[j-1] == arr[j]
          l_dups, r_dups = dups(arr, i, j)
          count += l_dups * r_dups * 2
          i += l_dups + 1
          j -= r_dups - 1
        elsif i != j and arr[j-1] == arr[j]
          count += 2
          j -= 1
        else
          count += 2
          i += 1
        end
      end
    elsif arr[i] + arr[j] < k
      i += 1
    else
      j -= 1
    end
  end
  count
end