Selection Sort - Ruby

#! /usr/bin/env ruby

# just input, ignore
puts "give me a string"
str = gets.chomp.split('')
strlen = str.length
# end of input section, stop ignoring

# begin sorting
for i in 0...strlen
    min_pos = i # assume the min element is the first element in the unsorted section of str

    for j in i+1...strlen # now loop through str, starting from i+1 since there is no need to reevaluate str[i]
        min_pos = j if (str[j] < str[min_pos]) # update min_pos if we find a smaller element
    end

    # now we swap them IF AND ONLY IF the smallest element in the unsorted portion of the array is not in its place yet
    # below you'll see the Ruby syntax for swapping two variables' values... it might look strange, but it actually
    # makes it stupidly simple
    str[i] , str[min_pos] = str[min_pos] , str[i] if min_pos != i
end

puts str.join('')