big-o/RotatingIterator.java at master · kowshik/big-o
* Implement a rotating iterator. The iterator accepts an array list of
* iterators, and iterates over them column-wise.
* * i.e If the following iterators are passed:
* * iterator_1 => [1] iterator_2 => [2, 3] iterator_3 => [4, 5]
* * Then the rotating iterator returns the following elements in sequential * order:
* * 1, 2, 4, 3, 5.
public class RotatingIterator<T> implements Iterator<T> {
private final ArrayList<Iterator<T>> iterators;
private int rotatingIndex;
private T nextItem;
public RotatingIterator(ArrayList<Iterator<T>> iterators) {
this.iterators = iterators;
this.rotatingIndex = 0;
}
@Override
public boolean hasNext() {
if (nextItem != null) {
return true;
}
int count = 0;
boolean itemFound = false;
while (!itemFound && count < iterators.size()) {
Iterator<T> iterator = iterators.get(rotatingIndex);
if (iterator != null && iterator.hasNext()) {
nextItem = iterator.next();
// we need this because nextItem can possibly be null.
itemFound = true;
}
rotatingIndex++;
rotatingIndex %= iterators.size();
count++;
}
return count != iterators.size();
}
@Override
public T next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
T toReturn = nextItem;
nextItem = null;
return toReturn;
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
}
Read full article from big-o/RotatingIterator.java at master · kowshik/big-o
* Implement a rotating iterator. The iterator accepts an array list of
* iterators, and iterates over them column-wise.
* * i.e If the following iterators are passed:
* * iterator_1 => [1] iterator_2 => [2, 3] iterator_3 => [4, 5]
* * Then the rotating iterator returns the following elements in sequential * order:
* * 1, 2, 4, 3, 5.
public class RotatingIterator<T> implements Iterator<T> {
private final ArrayList<Iterator<T>> iterators;
private int rotatingIndex;
private T nextItem;
public RotatingIterator(ArrayList<Iterator<T>> iterators) {
this.iterators = iterators;
this.rotatingIndex = 0;
}
@Override
public boolean hasNext() {
if (nextItem != null) {
return true;
}
int count = 0;
boolean itemFound = false;
while (!itemFound && count < iterators.size()) {
Iterator<T> iterator = iterators.get(rotatingIndex);
if (iterator != null && iterator.hasNext()) {
nextItem = iterator.next();
// we need this because nextItem can possibly be null.
itemFound = true;
}
rotatingIndex++;
rotatingIndex %= iterators.size();
count++;
}
return count != iterators.size();
}
@Override
public T next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
T toReturn = nextItem;
nextItem = null;
return toReturn;
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
}
Read full article from big-o/RotatingIterator.java at master · kowshik/big-o
