// Erika Wolfe, CSE 143
// This class represents a list of integers
// Note that LinkedIntList(int n) and addSorted(int value)
// would not likely be included in a real LinkedIntList 
// implementation, but are good examples to practice 
// LinkedIntList manipulation.
public class LinkedIntList {
    private ListNode front;
    
    // Constructs an empty list
    public LinkedIntList() {
        front = null;
    }
    
    // post: constructs a new list with the values 
    // [n, n-1, ..., 1, 0]
    public LinkedIntList(int n) {
        front = null;
        // we started by writing out each line explicitly        
        // front = new ListNode(0, front);
        // front = new ListNode(1, front);        
        // temp = new ListNode(2, front);
 
        for (int i = 0; i <= n; i++) {
            // you could also write this with a temp variable 
            // ListNode temp = new ListNode(i, front);
            // front = temp;
            
            front = new ListNode(n - i, front);
        } 
    }
    
    
    // pre : list is in sorted (non-decreasing) order
    // post: given value inserted into list so as to preserve sorted order
    public void addSorted(int n) {
        // the order of the tests is important! 
        if (front == null || front.data > n) {
            front = new ListNode(n, front);
        } else {
            ListNode current = front;
            //        robust test             sensitive test
            while (current.next != null && current.next.data < n) {
                current = current.next;
            }
            current.next = new ListNode(n, current.next);
        }
    }

    // pre: 0 <= index <= size 
    // post: inserts the given value at the given index, shifting subsequent
    //       values right                                       
    public void add(int index, int value) {                                              
        if (index == 0) {                                             
            front = new ListNode(value, front);                                              
        } else {                                                    
            // insert in middle/end; walk to node before the one to insert                               
            ListNode current = front;
            for (int i = 0; i < index - 1; i++) {
                current = current.next;
            }                 
            current.next = new ListNode(value, current.next);                                 
        }                                              
    }


    // post: appends the given value to the end of the list                                       
    public void add(int value) {   
        if (front == null) {                                                    
            front = new ListNode(value);                                     
        } else {                               
            ListNode current = front;                                                   
            while (current.next != null) {                                                   
                current = current.next;                                 
            }                             
            current.next = new ListNode(value);                                              
        }                               
    }                                 
}