ghost parser

ghost_thing.rb

class Array
	alias :peek :last
end
 
trials = gets.to_i
trials.times do |x|
	stack = []
	ctr = 0
	ptr = 0
	str = gets.chomp
	while ptr < str.length
		if str[ptr, 5] == "GHOST"
			ctr += 1
			ptr += 5
		elsif str[ptr,4] == "GHOS"
			stack.push("GHOS")
			ptr += 4
		elsif str[ptr,3] == "GHO"
			stack.push("GHO")
			ptr += 3
		elsif str[ptr,2] == "GH"
			stack.push("GH")
			ptr += 2
		elsif str[ptr,1] == "G"
			stack.push("G")
			ptr += 1
		elsif str[ptr,4] == "HOST" && stack.peek == "G"
			stack.pop
			ptr += 4
			ctr += 1
		elsif str[ptr,3] == "OST" && stack.peek == "GH"
			stack.pop
			ptr += 3
			ctr += 1
		elsif str[ptr,2] == "ST" && stack.peek == "GHO"
			stack.pop
			ptr += 2
			ctr += 1
		elsif str[ptr,1] == "T" && stack.peek == "GHOS"
			stack.pop
			ptr += 1
			ctr += 1
		else
			stack = []
			ptr += 1
		end
	end
	puts "Case #{x+1}: #{ctr}"
end