Optimization of search the most remote similar elements in an array

solution.rb

=begin
# Original algorithm

def solution(a)
  n = a.length
  result = 0
  for i in 0 .. (n - 1)
    for j in 0 .. (n - 1)
      if (a[i] == a[j]) then
        if (i - j).abs > result then
          result = (i - j).abs
        end
      end
    end
  end
  return result
end

=end

=begin
# 30% optimized algorithm

def solution(a)
  n = a.length
  result = 0
  for i in 0 .. (n - 1)
    break if n - 1 - i <= result
    for j in (n - 1) .. i
      break if j - i <= result
      if (a[i] == a[j]) then
        if j - i > result then
          result = j - i
        end
      end
    end
  end
  return result
end

=end

# Last algorithm

def solution(a)
  n = a.length
  result = 0
  h = {}
  (0..n - 1).each do |i|
    if h.key?(a[i])
      result = i - h[a[i]] if i - h[a[i]] > result
    else
      # save first entry of every unique value
      h[a[i]] = i
    end
  end
  result
end

a = [1, 2, 3, 4, 5, 6, 7, 8, 4, 9, 10]
b = [1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 2, 3, 4, 5, 3]
puts solution(a) # 5
puts solution(b) # 12