import java.util.NoSuchElementException;

// CSE 143, Autumn 2013
// A LinkedIntList object stores a list of integers using a series of linked                                         
// node objects.  We will implement the same methods as ArrayIntList.  

public class LinkedIntList {
	private ListNode front;     // refers to first node in list (null if empty)

	// Constructs a new empty list.
    public LinkedIntList() {
        front = null;
    }

    // Adds the given value to the end of this list.
    public void add(int value) {
    	if (front == null) {
    		// empty list
    		front = new ListNode(value);
    	} else {
    		// non-empty list; walk to last node
    		ListNode current = front;
    		while(current.next != null) {
    			current = current.next;
    		}
    		// add new node at end of list
    		current.next = new ListNode(value);
    	}	
    }
    
    // Adds a value at a given index.
    // pre: 0 <= index <= size
    public void add(int index, int value) {
    	if (index == 0) {
    		front = new ListNode(value, front);
    	} else {
	    	ListNode current = front;
	    	for(int i = 0; i < index - 1; i++) {
	    		current = current.next;
	    	}
	    	current.next = new ListNode(value, current.next);
    	}
    }
    
    // removes and returns the first element in the list
    // Pre: size > 0
    public int remove() {
    	if (front == null) {
    		throw new NoSuchElementException(); 
    	}
    	int value = front.data;
    	front = front.next;
    	return value;
    }
    
    // Removes the value at the given index.
    // Pre: 0 <= index < size
    public void remove(int index) {
    	if (index == 0) {
    		front = front.next;
    	} else {
	    	ListNode current = front;
	    	for(int i = 0; i < index - 1; i++) {
	    		current = current.next;
	    	}
	    	current.next = current.next.next;
    	}
    	
    }
    
    // Returns the element at the specified index from the list.
    // Precondition: 0 <= index < size
    public int get(int index) {
    	ListNode current = front;
    	for(int i = 0; i < index; i++) {
    		current = current.next;
    	}
    	return current.data;
    }
    
    // pre: list is sorted
    // post: list is sorted and the given value is added in sorted order, duplicates allowed.
    public void addSorted(int value) {
    	if (front == null || value < front.data) {
    		front = new ListNode(value, front);
    	} else {
    		ListNode current = front;
    		while (current.next != null && current.next.data < value) {
    			current = current.next;
    		}
    		current.next = new ListNode(value, current.next);
    	}
    }
	
    // Returns a comma-separated String representation of this list.
    public String toString() {
    	if (front == null) {
    		return "[]";
    	} else {
    		String result = "[" + front.data;
    		ListNode current = front.next;
    		while (current != null) {
    			result += ", " + current.data;
    			current = current.next;
    		}
    		result += "]";
    		return result;
    	}
    }
}