Bubble Sort - Ruby

#! /usr/bin/env ruby

# get input
puts "give me a string"
str = gets.chomp.split('')
strlen = str.length
# end get input

changes_made = false #optimization to reduce time complexity

for i in 0..(strlen - 2) # vvv
# 0 thru two less than the length of str, because we never need to see the last element explicitly
# because we reach later on with str[j+1]

    for j in 0..(strlen - 2)

        if str[j] > str[j+1]
            str[j],str[j+1] = str[j+1],str[j] # Ruby way to swap vars
            changes_made = true # record that a change was made in this runthrough
        end

    end

    break if !changes_made
    # if there were no changes this run, the list is sorted
    # why continue "sorting" if we've already done the job?

    # if there was a change made, set that to false and run through again,
    # unless, of course, we've already gone through
    changes_made = false
end

puts str.join('') #print out the result, but first make it a string and not an array