[CC150][2.1] Write code to remove duplicates from an unsorted linked list.

rmDuplicate.java

import java.util.LinkedList;
import java.util.HashSet;

public class rmDuplicate {

	//* why return a new LinkedList rather than modifiying the original one?
	//* remove(object) in LinkedList(Java) could be O(N) in worst case (i.e. closer to tail of the LinkedList)
	//* for LinkedList [1,1,...,1,1,1] (length N), remove dupicate elements would cost (1+2+...+N-1) ~ O(N^2)
	//* write your own LinkedList where you can manipulate the reference could solve the problem
	public static<Item> LinkedList<Item> rm (LinkedList<Item> list) {
		HashSet<Item> set = new HashSet<Item>();
		LinkedList<Item> newList = new LinkedList<Item>();
		for (Item item : list)
			if (set.add(item))
				newList.add(item);
		return newList;
	}
	
	public static void main (String[] args) {
		LinkedList<Integer> testA = new LinkedList<Integer>();
		for (int i = 0; i < 5; i++)
			testA.add(i);
		for (int i = 10; i > 0; i--)
			testA.add(i);
		System.out.println(testA.toString());
		System.out.println(rmDuplicate.rm(testA).toString());
	}
}