# 0 1 2 3 4 5 6
input = [1,2,4,2,5,3,5]
def duplicates(input)
hash = Hash.new(0)
output = Hash.new([])
input.each do |n|
hash[n] += 1
end
hash.each do |k,v|
if v > 1
output[k] = []
input.each_with_index do |e, i|
if e == k
output[k] << i
end
end
end
end
output
end
p duplicates(input)
