Sorting String Array Indicies with Insertion Sort, Doubly Linked List

Question

I am working on an assignment where I have to sort an array and store the indices in a doubly linked list ADT that I have built.

Example:
{"A","B","C","A"} -> {0,3,1,2}

My current approach is to bring the indices into my ADT and then sort the ADT as I sort the array. As far as I can tell, I am doing the exact same operation on both the array and the doubly linked list every time either loop executes, but my output does not match up.

public static void main(String[] args ) {
    List A = new List();
    String[] inputArray = {"A","C","B","A"};
    int i,j;
    String key;
    //load indices into doubly-linked list
    for (int x = 0; x < inputArray.length; x++ ) {
        A.append(x);
    }
    //begin insertion sort
    for (j = 1; j < inputArray.length; j++) {
        System.out.println(A);
        System.out.println(Arrays.toString(inputArray));
        key = inputArray[j];
        i = j - 1;
        while (i >= 0) {
            if (key.compareTo(inputArray[i]) > 0) {
                break;
            }
            inputArray[i+1] = inputArray[i];
            //moveTo moves the cursor to <int>
            A.moveTo(i);
            //make sure we aren't trying to insert before first node
            if (i > 0) { A.insertBefore(i+1); }
            else { A.prepend(i+1); }
            //remove node at cursor
            A.delete();
            i--;
        }
        inputArray[i+1] = key;
        A.moveTo(i+1);
        if (i > 0) { A.insertBefore(i+1); }
        else { A.prepend(i+1); }
        A.delete();
    }
    System.out.println(A);
    System.out.println(Arrays.toString(inputArray));
}

The above code gives the following output:

run:
0 1 2 3
[A, C, B, A]
1 0 2 3
[A, C, B, A]
1 1 2 3
[A, B, C, A]
0 2 3 3
[A, A, B, C]
BUILD SUCCESSFUL (total time: 0 seconds)

EDIT: List.java

public class List {

    private class Node{
        //Fields
        int data;
        Node next, previous;
        //Constructor
        Node(int data) {
            this.data = data;
            next = null;
            previous = null;
        }
        public String toString() { return String.valueOf(data); }
    }

    //Fields
    private Node frontNode, backNode, cursorNode;
    private int totalSize, cursorPosition;

    //Constructor
    List() {
        frontNode = backNode = cursorNode = null;
        totalSize = 0;
        cursorPosition = -1;
    }
    //moveTo(int i): If 0<=i<=length()-1, moves the cursor to the element 
    // at index i, otherwise the cursor becomes undefined.
    void moveTo(int i) {
        if (i == 0) {
            cursorPosition = i;
            cursorNode = frontNode;
        }
        else if (i == length() - 1) {
            cursorPosition = i;
            cursorNode = backNode;
        }
        else if (i > 0 && i < length() - 1 ) {
            cursorNode = frontNode;
            cursorPosition = i;
            for (int x=0; x < i; x++) {
                cursorNode = cursorNode.next;
            }
        }
        else {
            cursorPosition = -1; 
        }
    }

//prepend(int data): Inserts new element before front element in this List.
    void prepend(int data) {
        Node node = new Node(data);
        if ( this.length() == 0 ) {
            frontNode = backNode = node;
        }
        else {
            frontNode.previous = node;
            node.next = frontNode;
            frontNode = node;
        }
        totalSize++;
        //cursorPosition might change?
    }
    //insertBefore(int data): Inserts new element before cursor element in this
    // List. Pre: length()>0, getIndex()>=0
    void insertBefore(int data) {
        Node node = new Node(data);
        if ( this.length() > 0 && this.getIndex() >= 0 ) {
            node.previous = cursorNode.previous;
            node.next = cursorNode;
            cursorNode.previous.next = node;
            cursorNode.previous = node;
            totalSize++;
        }
        else if ( this.length() <= 0 )
        {
           throw new RuntimeException
                    ("Error: insertBefore called on empty list");
        }
        else {
            throw new RuntimeException
                    ("Error: insertBefore called without cursor set");
        }
    }

Answer 1

OK, thanks. I didn't know exactly what insertBefore() and prepend() were intended to do (I could have guessed, but programming should not be about guessing what methods are supposed to do; seeing the documentation is much better).

Since this is an assignment, I'm not going to give you the answer. But the clue is this: After the first pass through the loop, the dump of A gives you the same indices you started with, but rearranged. I think that's the way it's supposed to be after every loop iteration. But that's not true after the second pass through the loop (1 shows up twice, and 0 is gone). Think about it. When you called A.insertBefore() to rearrange the elements of A, what data should you have told insertBefore() to insert, and what did you actually insert?