import java.io.*;


/*
* 
*
*
*
*
*
* Modified methods
* ----------------
*
* str_write(): recursion replaced with a while loop
* str_length(): recursion replaced with a while loop
* str_extract(): recursion replaced with a while loop
* str_index(): recursion replaced with a while loop
* str_concat(): recursion replaced with a for loop
*	that uses the value returned from str_length() as
* str_delete(): This one is a little complecated. Since the
*	the list is generated backwards by the method
*	I wrote I had to reverse is again before returning it.
*	The recursion has been replaced mainly with a while loop.
*
*/




public class LLString
{
	private char first;
	private LLString next;


	public LLString(char c, LLString s)
	{
		first = c;
		next = s;	
	}

	public LLString()
	{
		first = ' ';
		next = null;	
	}

	public LLString(String s)
	{
		StringBuffer sbuff = new StringBuffer(s);
		LLString result = null;
		for(int pos = sbuff.length() - 1; pos > 0; pos--)
			result = new LLString(sbuff.charAt(pos), result);
		next = result;
		first = sbuff.charAt(0);
	}

	void str_write()
	{	
		
		LLString current;
		current = next;	

		System.out.print(first);

		while(current != null){		
			System.out.print(current.first);
			current = current.next;
		}
			System.out.println("");
		

		
		//All old code commented out for easy testing
		/*
		System.out.print(first);
		if(next == null)
			System.out.println("");
		else
			next.str_write();
		*/

	}

	int str_length()
	{
		LLString current;
		current = next;	
		int size = 1;
		
		while(current != null){		
			size++;
			current = current.next;
		}
		return size;
	

		//All old code commented out for easy testing
		/*
		if(next == null)
			return 1;
		else
			return (1 + next.str_length());
		*/
	}

	char str_extract(int pos)
	{
		LLString current;		
		int count=0;
		if(pos == count){
			return this.first;
		}else{
		current = next;
			while(current != null){
				count++;
				if(count == pos){
					return current.first;
				}
				current = current.next;
			}
			return  '\0';
		}


		//All old code commented out for easy testing
		/*
		if(pos == 0)
			return this.first;			
		else if (next == null)
			return (char)0;
		else
			return next.str_extract(pos-1);	
		*/

	}
	
	int str_index(char c)
	{

		LLString current;
		int pos = 0;
		if(first == c){
			return pos;
		}else{
		current = next;
			while(current != null){
				pos++;
				if(current.first == c){
					return pos;
				}
				current = current.next;
			}
			return  -1;
		}
		

		//All old code commented out for easy testing
		/*
		if(c == first)
			return 0;
		else if(next == null)
			return - 1;
		else
		{
			int pos = next.str_index(c);

			if(pos == -1)
				return -1;
			else
				return pos + 1;
		}
		*/

	}	

	LLString str_concat(LLString nextString)
	{	
		LLString current;		
		current = next;
		int size = next.str_length();

		for(int i = 0;i<size;i++){
			if(current.next == null){
				current.next = nextString;
			}else{
			current = current.next;
			}
		}
		return this;


		//All old code commented out for easy testing
		/*
		if(next == null)
			next = nextString;
		else
			next.str_concat(nextString);
		return this;
		*/
		

	}	

	LLString str_delete(char ch)
	{
		LLString current;
		boolean found = false;
		//this.str_write();
		
		LLString temp = new LLString(first, null);
		if(first == ch){
			current = next;
			return current;
		}else{
			current = next;
			while(current != null){
				if(current.first != ch){
					temp = new LLString(current.first, temp);
				}else{
					found = true;
					//temp = new LLString(current.first, temp);
				}	
				current = current.next;
			}


			if(found == false){
				return this;
			}else{
				LLString temp2 = new LLString(temp.first, null);
				current = temp.next;
				while(current != null){
					temp2 = new LLString(current.first, temp2);
					current = current.next;
				}
				return temp2;
			}

		}


		//All old code commented out for easy testing
		/*
		if(first == ch)
			return next;
		else if(next == null)
			return this;
		else
		{
			next = next.str_delete(ch);
			return this;
		}
		
		*/

	}


	public static void main(String args[])
	{

		LLString s = new LLString('e', null);
		s.str_write();
		
		s = new LLString('n', s);
		s.str_write();

		s = new LLString('o', s);
		s.str_write();
		System.out.println(s.str_length());
		
		LLString v = new LLString("Test Case");
		v.str_write();
		
		System.out.print("Delete T: ");
		v = v.str_delete('T');
		v.str_write();

		System.out.print("Delete e: ");
		v = v.str_delete('e');
		v.str_write();
		
		System.out.print("Delete e: ");
		v = v.str_delete('e');
		v.str_write();

		System.out.print("Delete e: ");
		v = v.str_delete('e');
		v.str_write();
		
		v = new LLString("Can you ");
		v.str_write();
	
		LLString w = new LLString("Concat");
		w.str_write();
		
		v = v.str_concat(w);
		v.str_write();
		
		System.out.println("Extract character 11: " + v.str_extract(11));
		System.out.println("Index of o: " + v.str_index('o'));
		System.out.println("Index of c: " + v.str_index('c'));
		System.out.println("Index of t: " + v.str_index('t'));

	}//end main


}//end class LLString