Reverse sentence

# ----------------------------------------------------- #
# Roel Castaño Moreno.									#
# March 21, 2014.										#
# Problem 2 for Icalia Labs.							#
# ----------------------------------------------------- #


# Function that reverses the string "str"
def reverse_words(str)

	# Variable that stores location of space
	sp = str.index(" ")
	# Variable that stores start of the next word to reverse
	st = 0

	# Iterates through the spaces in the sentence while it finds spaces
	while (sp != nil)

		# Stored location of the center of the sentence
		middle = (sp-st) / 2

		# Iterates through word inverting the letters
		middle.times do |i| 
			str[st], str[sp-(i+1)] = str[sp-(i+1)], str[st] 
			st = st + 1
		end

		# Stored start of next word
		st = sp + 1
		# Looks for the next space
		sp = str.index(" ", sp+1)
	end

	# Reverses last word
	sp = str.length
	middle = (sp - st) / 2
	middle.times do |i| 
		str[st], str[sp-(i+1)] = str[sp-(i+1)], str[st] 
		st = st + 1
	end

end


# Asks for user's input (sentence to be processed).
print "Please write a sentence: "
sentence = gets.chomp

# Input sentence into function to be reversed
reverse_words(sentence)

# Print reversed sentence
puts sentence