String Encoding - Character Count

String encoding - character count

str = 'aaaabbbccddddd'
out = ''
Stack s = new Stack()

i=0
while(i<str.length()){

	//if element matched
	if(!s.empty() && s.peek() !=  str[i] ){
		out = out +  s.peek() + '' + s.size()
		//empty the stack
		s = new Stack()
	}

	//push to stack
	s.push(str[i])
	i++
}

//for last pattern
if(i == str.length()){
	out = out +  s.peek() + '' + s.size()
}

println out