Amazon Interview Question for Interns


Country: United States
Interview Type: Phone Interview




Comment hidden because of low score. Click to expand.
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of 0 vote

import java.util.ArrayList;
import java.util.Iterator;

public class Problem<E> implements Iterator<E> {
	Iterator<Iterator<E>> iter;
	Iterator<E> iter2;

	Problem(Iterator<Iterator<E>> iter) {
		this.iter = iter;
		if (iter.hasNext())
			this.iter2 = iter.next();
	}

	@Override
	public boolean hasNext() {
		if (iter2 != null) {
			if (iter2.hasNext())
				return true;
		}
		while (iter.hasNext()) {
			iter2 = iter.next();
			if (iter2.hasNext())
				return true;
		}
		return false;
	}

	@Override
	public E next() {
		if (iter2 != null) {
			if (iter2.hasNext())
				return iter2.next();
		}
		if (iter.hasNext()) {
			iter2 = iter.next();
			return this.next();
		}
		return null;
	}

	@Override
	public void remove() {
		// TODO Auto-generated method stub

	}

	public static void main(String[] args) {
		// I am making an iterator of iterator here.
		ArrayList<ArrayList<Integer>> integers = new ArrayList<ArrayList<Integer>>();
		for (int i = 0; i < 10; i++) {
			ArrayList<Integer> temp = new ArrayList<Integer>();
			for (int j = 0; j < i; j++) {
				temp.add(i);
			}
			integers.add(temp);
		}
		ArrayList<Iterator<Integer>> iter = new ArrayList<Iterator<Integer>>();
		for (int i = 0; i < integers.size(); i++) {
			iter.add(integers.get(i).iterator());
		}
		Iterator<Iterator<Integer>> iterator = iter.iterator();

		// Now I pass the iterator of iterator to the class problem. Problem is
		// actually an iterator since I implement Iterator<Integer>
		@SuppressWarnings({ "rawtypes", "unchecked" })
		Problem p = new Problem(iterator);
		while (p.hasNext()) {
			System.out.println(p.next());
		}
	}

}

- mahdi.oraei February 26, 2014 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

import java.util.Arrays;
import java.util.Iterator;

public class FlattedIterator<E> implements Iterator<E> {

	private final Iterator<? extends Iterator<? extends E>> nested;
	private Iterator<? extends E> cur;

	public FlattedIterator(Iterator<? extends Iterator<? extends E>> nested) {
		this.nested = nested;
		cur = nested.next();
	}

	public static <E> Iterator<E> flattern(Iterator<? extends Iterator<? extends E>> nested) {
		return new FlattedIterator<E>(nested);
	}

	@Override
	public E next() {
		if (!hasNext()) {
			return null;
		}
		return cur.next();
	}

	@Override
	public boolean hasNext() {
		while (cur != null) {
			if (cur.hasNext()) {
				return true;
			}
			if (nested.hasNext()) {
				cur = nested.next();
			} else {
				return false;
			}
		}
		return false;
	}

	@Override
	public void remove() {
		if (cur.hasNext()) {
			cur.remove();
		}
	}

	public static void main(String[] args) {
		Iterator<Integer> a = Arrays.asList(1, 2, 3).iterator();
		Iterator<Double> b = Arrays.asList(4.0, 5.0, 6.0).iterator();
		Iterator<Long> c = Arrays.asList(7L, 8L, 9L).iterator();
		Iterator<? extends Iterator<? extends Number>> list = Arrays.asList(a, b, c).iterator();

		Iterator<Number> itr = flattern(list);
		while (itr.hasNext()) {
			Number num = itr.next();
			System.out.println(num);
		}

	}
}

- ttoommbb@126.com August 24, 2014 | Flag Reply


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