Results 1 to 2 of 2
Thread: Linked List swapping question
 02192012, 11:33 AM #1Member
 Join Date
 Aug 2011
 Posts
 16
 Rep Power
 0
Linked List swapping question
The question goes like this
Swaps two elements in the list,
* list: A B C > swap(A,B) will result in the list B A C
* list: A C C > swap(A, D) will throw a NoSuchElementException
* list: A B C B > swap (A, B) will result in the list B A C B
* list: A B C A B B > swap (A,B) will result in the list B A C A B B
* a list with one or zero elements cannot do a swap
I'm really out of wits and ran out of patience with this question, I've made a working version but just changing the values is not allowed and I have to relink them manually. I spend already 10 hours on figuring out how to relink them. I'm sick of my lecturer he just threw everything to us without explaining and my classmates would not help.
I've checked out the internet all over but failed to understand why. This is my last resort.
Java Code:import java.util.NoSuchElementException; public class SwapListImpl<T> implements SwapList<T> { int size=0; Node<T> first; Node<T> last; Node<T> list; Node<T> swapNode = new Node(0); public void add(T val) { if(size==0) { first = new Node<T>(val); // last = first; // size++; // } else { if(size==1) { list = new Node<T>(val); last.prev = first; last.next = list; list.prev = first; last = list; size++; }else{ Node<T> nNode=new Node<T>(val); nNode.prev=last; last.next=nNode; last=nNode; size++; } } } public T get(int i) { Node<T> temp = first; for(int x=0; x<i;x++) { temp=temp.next; } return temp.val; } public void swap(T val1, T val2) { swap2(val1, val2); } public void swap2(T val1, T val2) throws NoSuchElementException { Node<T> elementA=first; Node<T> elementB=first; boolean found = false; int i =0; int x =0; if(size>1) { while(!elementA.val.equals(val1) && elementA.next!=null) { elementA=elementA.next; i++; } while(!elementB.val.equals(val2) && elementB.next!=null) { elementB=elementB.next; x++; } if(!elementA.val.equals(val1) && !elementA.equals(val2)  !elementB.val.equals(val1) && !elementB.val.equals(val2)) { throw new NoSuchElementException(); } // I found the two nodes to swap but I cant ever get past the relink process // swapNode.prev = elementA.prev; // swapNode.next = elementB.prev; // System.out.println(swapNode.prev.val+" "+swapNode.next.val); } } }
Last edited by FiasseKrystella; 02192012 at 11:35 AM.
 02192012, 12:35 PM #2
 Join Date
 Sep 2008
 Location
 Voorschoten, the Netherlands
 Posts
 14,321
 Blog Entries
 7
 Rep Power
 25
Re: Linked List swapping question
Think of the elements before nodes A and B, say prevA and prevB. Also think of the elements following A and B, say nextA and nextB. So prevA and nextA embrace element A an similar with prevB, nextB and B. Swapping elements A and B is just updating all the pointers in the nodes:
Java Code:prevA.next= B; nextA.prev= B; B.prev= prevA; B.next= nextA; prevB.next= A; nextB.prev= A; A.prev= prevB; A.next= nextB;
JosThe only person who got everything done by Friday was Robinson Crusoe.
Similar Threads

a linked list question
By smacker in forum New To JavaReplies: 5Last Post: 05042011, 12:57 PM 
n00b: linked list question
By ankitmcgill in forum New To JavaReplies: 2Last Post: 03132009, 05:15 AM 
[SOLVED] Linked list question
By ztrath in forum New To JavaReplies: 8Last Post: 03122009, 12:38 AM 
Revised Linked List printing method question
By CirKuT in forum New To JavaReplies: 7Last Post: 12122008, 11:21 PM 
Linked List Question
By CirKuT in forum New To JavaReplies: 4Last Post: 12102008, 07:56 PM
Bookmarks