First Duplicate Challenge

first_duplicate.rb

require 'pry'

def first_duplicate1(a)
    counts = []
    a.each_with_index do |value, i|
        return value if counts[value]
        counts[value] = true
        binding.pry
    end
    -1
end


def first_duplicate2(a)
    a.each do |value|
        return value.abs if a[value.abs - 1] < 0
        a[value.abs - 1] = -a[value.abs - 1]
    end
    -1
end

array1 = [2, 3, 3, 1, 5, 2]
array2 = [2, 4, 3, 5, 1]
array3 = [1]
array4 = [8, 4, 7, 9, 5, 6, 2, 6, 4, 8]

# puts first_duplicate1(array1) == 3;
# puts first_duplicate1(array2) == -1;
# puts first_duplicate1(array3) == -1;
puts first_duplicate1(array4) == 6;
#
# puts first_duplicate2(array1) == 3;
# puts first_duplicate2(array2) == -1;
# puts first_duplicate2(array3) == -1;
# puts first_duplicate2(array4) == 6;