CareerCup

this would only cater for the case of finding "direct" children/parents, the questions of the OP says "all the children nodes and all the parents"...

Hi guys,

why over complicating it so much. The op just asks for flattening a list of lists of integers and implementing next and hasNext. No need for implementing Iterator thus far. Just forward requests to a backing list that just encapsulates the list of lists.

public class FlattenList {
	int index = 0;
	List<Integer> flattenedList = new ArrayList<>();
	
	private FlattenList(){
	}
	
	public static FlattenList getList(List<List<Integer>> lists){
		FlattenList flattenList = new FlattenList();
		flattenList.flatten(lists);
		return flattenList;
	}

	private void flatten(List<List<Integer>> lists) {
		for(List<Integer> list : lists){
			flattenedList.addAll(list);
		}
	}
	
	public boolean hasNext(){
		return flattenedList.size() > index; 
	}
	
	public Integer next(){
		Integer result = flattenedList.get(index);
		index++;
		return result;
	}
}

and the test should look like this

public class FlattenListTest {

	@Before
	public void setUp() throws Exception {
	}

	@Test
	public void test() {
		
		FlattenList flattenList = FlattenList.getList(Arrays.asList(
				Arrays.asList(6, 8),
				Arrays.asList(4)
		));
		
		assertEquals(new Integer(6), flattenList.next());
		assertEquals(new Integer(8), flattenList.next());
		assertEquals(new Integer(4), flattenList.next());
		assertEquals(false, flattenList.hasNext());
		
	}

}