Question

So this code will count the total number of pairs of numbers whose difference is K. it is naive method and I need to optimize it. suggestions?

test = $stdin.readlines 

input = test[0].split(" ")

numbers = test[1].split(" ")

N = input[0]
K = input[1]

count = 0

for i in numbers
   current = i.to_i
   numbers.shift
   for j in numbers
       difference = (j.to_i - current).abs
       if (difference == K)
           count += 1
       end
   end
end

puts count

Answer 1

Would have been nice for you to give some examples of input and output, but I think this is correct.

require 'set'

def count_diff(numbers, difference)
  set = Set.new numbers
  set.inject 0 do |count, num|
    set.include?(num+difference) ? count+1 : count
  end
end


difference  =  gets.split[1].to_i
numbers     =  gets.split.map { |num| num.to_i }

puts count_diff(numbers, difference)