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POFinding duplicates in sorted, linked list
 

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  1. POFinding duplicates in sorted, linked list
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    <p>I've created a sorted linked list and now I'm trying to figure out how to remove duplicates. I wanted to add code that would do this in the Add method I created but I can't seem to figure it out. I feel like this should be relatively easy but I'm a bit brain dead right now.</p> <p>In my add method I check the index to see where an item is to be added. "Index" is an int variable but I wanted to check to see if "item", a comparable, was the same item stored before it. I wanted to use the compareTo method but I would get a type mismatch. Does anyone have an idea of a better way to do this?</p> <p>Here is the code for my add method:</p> <pre><code> package sortedListReferenceBased; public class SortedListReferenceBasedIterativeNoDuplicates implements SortedListInterface { // reference to linked list of items private Node head; private int numItems; // number of items in list public SortedListReferenceBasedIterativeNoDuplicates() { numItems = 0; head = null; } // end default constructor public boolean sortedIsEmpty() { return numItems == 0; //TODO } // end sortedIsEmpty public int sortedSize() { return numItems; //TODO } // end sortedSize private Node find(int index) { // -------------------------------------------------- // Locates a specified node in a linked list. // Precondition: index is the number of the desired // node. Assumes that 1 &lt;= index &lt;= numItems+1 // Postcondition: Returns a reference to the desired // node. // -------------------------------------------------- Node curr = head; for (int skip = 1; skip &lt; index; skip++) { curr = curr.getNext(); } // end for return curr; } // end find public Comparable sortedGet(int index) throws ListIndexOutOfBoundsException { if (index &gt;= 1 &amp;&amp; index &lt;= numItems){ Node curr = find(index); Object dataItem = curr.getItem(); return (Comparable) dataItem; } else { throw new ListIndexOutOfBoundsException("List index out of bounds on get."); } //TODO } // end sortedGet() public void sortedAdd(Comparable item) throws ListException{ int index = locateIndex(item); //to find location where item should be added if( index &gt;=1 &amp;&amp; index &lt;= numItems+1){ //if adding an item to the very beginning of list if (index == 1){ Node newNode = new Node(item,head); head = newNode; } if (item.compareTo(something something?)== 0){ //if item is a duplicate of previous item do nothing System.out.println("No duplicates!"); } //advances else { Node prev = find(index-1); //finds out where previous node is Node newNode = new Node(item, prev.getNext()); //creates Node with item you wish to add prev.setNext(newNode); //links new node with previous node } numItems++; }//end main if statement else { throw new ListIndexOutOfBoundsException("List index out of bounds on add."); } //TODO } // end sortedAdd() public void sortedRemove(Comparable item) throws ListException { int index = locateIndex(item); if (index &gt;= 1 &amp;&amp; index &lt;= numItems){ //if the index is greater than 1 (meaning list not empty) and //index doesn't exceed list size do the following: //if index is value of one then delete first node in this special way if (index == 1) { head = head.getNext(); } //if there is only one item in the list then set head to nothing so index out of bounds error won't occur if (numItems == 1){ head = null; } else { //if none of these things occur go ahead and delete item, allocating Nodes accordingly Node prev = find(index-1); Node curr = prev.getNext(); prev.setNext(curr.getNext()); } numItems--;//must account for one less item } if (!sortedIsEmpty()){ System.out.println("Item does not exist!"); } else { //if index doesn't meet if statement requirements throw new ListIndexOutOfBoundsException("List index out of bounds on remove."); } //TODO } // end sortedRemove public void sortedRemoveAll() { // setting head to null causes list to be // unreachable and thus marked for garbage // collection head = null; numItems = 0; } // end sortedRemoveAll //Returns the position where item belongs or exists in a sorted list; //item and the list are unchanged. public int locateIndex(Comparable item) { Node curr = head; for (int i = 1; i &lt;= sortedSize(); i++){ if (item.compareTo(curr.getItem())&lt;= 0){ return i; }//end if else { curr = curr.getNext(); }//end else }//end for return sortedSize()+1; //TODO } //end locateIndex() } // end ListReferenceBased </code></pre> <p>I apologize for the strange formatting. It's pretty rough right now. I also apologize if this question is really obvious! Haha</p>
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