Find the smallest index in an array where all array values exist prior to index

gistfile1.rb

def ps(list)

  freq = {}

  list.each do |v|
    freq[v] = 0 if freq[v].nil?
    freq[v] += 1
  end

  list.each_with_index do |v, i|
    freq.delete(v)
    if freq.empty?
      return i
    end
  end

  return list.size - 1

end

class TestPs < Test::Unit::TestCase

  def test_one
    arr = [ 2, 2, 1, 0, 1 ]
    assert_equal(ps(arr), 3)
  end

  def test_two
    arr = [ 1, 0 ]
    assert_equal(ps(arr), 1)
  end

  def test_three
    arr = [ 1, 2, 3, 3, 3, 3, 10, 11, 9 ]
    assert_equal(ps(arr), 8)
  end

end