https://xmruibi.gitbooks.io/interview-preparation-notes/content/DataStructure/Iterator/JumpIterator.html
https://xmruibi.gitbooks.io/interview-preparation-notes/content/DataStructure/Iterator/EvenIterator.html
Implements an iterator only output the even number.
https://xmruibi.gitbooks.io/interview-preparation-notes/content/DataStructure/Iterator/IteratorFor2DArray.html
Set up a iterator to iterate a 2-dimensional array.
Iterator for 2-D Array
Given a Iterator which contain several iterator inside. The task is to iterate all elements inside these iterators
Implements an iterator in each output it print the number and skip the next one.
public class JumpIterator implements Iterator<Integer> {
Iterator<Integer> iterator;
public JumpIterator(Iterator<Integer> iterator) {
this.iterator = iterator;
}
@Override
public boolean hasNext() {
return iterator.hasNext();
}
@Override
public Integer next() {
int res = iterator.next();
if (iterator.hasNext())
iterator.next();
return res;
}
}https://xmruibi.gitbooks.io/interview-preparation-notes/content/DataStructure/Iterator/EvenIterator.html
Implements an iterator only output the even number.
public class EvenIterator implements Iterator<Integer> {
Iterator<Integer> iterator;
public EvenIterator(Iterator<Integer> iterator) {
this.iterator = iterator;
}
@Override
public boolean hasNext() {
return iterator.hasNext(); // should put while logic here
}
@Override
public Integer next() {
int res = 0;
while (iterator.hasNext() && (res = iterator.next()) % 2 != 0)
;
return res;
}
}https://xmruibi.gitbooks.io/interview-preparation-notes/content/DataStructure/Iterator/IteratorFor2DArray.html
Set up a iterator to iterate a 2-dimensional array.
Iterator for 2-D Array
- Iterate the 2-D array by
xandy. - Record current element during
hasNext()function. - Check the row if it is null.
public class DeepIterator{
int cur; // this is important
int row = 0, col = 0;
int[][] listOfLists;
public DeepIterator(int[][] listOfLists){
if(listOfLists == null)
throw new IllegalArgumentException("Null Input");
this.listOfLists = listOfLists;
}
public Integer next(){
return cur;
}
public boolean hasNext(){
// make sure the row is not null
while(row < listOfLists.length && col >= listOfLists[row].length) {
row ++; col = 0;
}
if(row < listOfLists.length) {
cur = listOfLists[row][col++];
return true;
}else
return false;
}
public static void main(String[] args) {
int[][] listOfLists = {
{},{},{1,2,3},{},{},{2,3,4}
};
DeepIterator it = new DeepIterator(listOfLists);
while(it.hasNext()){
System.out.println(it.next());
}
}
}Given a Iterator which contain several iterator inside. The task is to iterate all elements inside these iterators
- It's a class implements iterator interface but also contains several iterators.
- Image these iterator is a bucket, the unit is a iterator and the cursor of bucket index is a iterator
element. - Set a current index to point at a iterator.
public class Iterators<T> implements Iterator<T>{
Iterators<T> current;
Iterators<Iterators<T>> cursor;
public Iterators(Iterable<Iterator<T>> iterators){
if(iterators == null)
throw new IllegalArgumentException("Illegal Argument!");
this.cursor = iterators;
}
@Override
public T next(){
return current.next();
}
@Override
public boolean hasNext(){
if(!current.hasNext())
current = findNext();
return current != null && current.hasNext();
}
private Iterator findNext(){
while(cursor.hasNext()){
current = cursor.next();
if(current != null && current.hasNext())
break;
}
return current;
}
@Override
public void remove(){
if(current!=null)
current.remove();
}
}
Given an Iterator class interface with methods:
next() and hasNext(), design and implement a PeekingIterator that support the peek() operation -- it essentially peek() at the element that will be returned by the next call to next().class PeekingIterator implements Iterator<Integer> {
int cur;
Iterator<Integer> it;
public PeekingIterator(Iterator<Integer> iterator) {
this.it = iterator;
cur = it.hasNext() ? it.next() : null; //\\
}
// Returns the next element in the iteration without advancing the iterator.
public Integer peek() {
return cur;
}
// hasNext() and next() should behave the same as in the Iterator interface.
// Override them if needed.
@Override
public Integer next() {
int res = curl
cur = it.next() ? it.next() : null;
return res;
}
@Override
public boolean hasNext() {
return it.hasNext();
}
}