search_pairs.rb

def pairs(numbers, diff)
  counter = 0
  numbers.sort!
  n = numbers.length
  numbers.each_with_index do |val, i|
    j = i + 1
    subject = val + diff
    j += 1 while j < n && numbers[j] < subject

    while numbers[j] == subject
      counter += 1
      j += 1
    end
  end
  puts counter
end

n, k = gets.split.map!(&:to_i)
numbers = gets.split(" ").map!(&:to_i)
pairs(numbers, k)