Interview Question for Java Developers


Country: United States
Interview Type: Phone Interview




Comment hidden because of low score. Click to expand.
2
of 2 vote

This can be done, by maintaining a min heap of elements and its associated iterator index in a struct.
hasNext - returns if there are any elements in min heap
next fetches the top element in minheap , and then grabs its iterator and checks if it has any element if so add it to the minheap.

private class minHeapElement {
int index;
int value;
}
PriorityQueue<minHeapElement> minHeap = new PriorityQueue(iters.size(), (a,b)-> a.value-b.value );

- Anonymous March 21, 2018 | Flag Reply
Comment hidden because of low score. Click to expand.
1
of 1 vote

This is just "merge k sorted arrays". Use merge sort.

- Basmati March 21, 2018 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

Use a priority queue and insert elements into the queue as you go along and call next. Posting my solution below in Python:

from queue import PriorityQueue

class SuperIterator:
  def __init__(self, iterators):
    self.sortedQueue = PriorityQueue()
    for iterator in iterators:
      self.sortedQueue.put((next(iterator), iterator))

  def hasNext(self):
    return self.sortedQueue.qsize() != 0

  def next(self):
    value, iterator = self.sortedQueue.get()
    try:
      next_value = next(iterator)
      self.sortedQueue.put((next_value, iterator))
    except StopIteration:
      pass
    return value

Test code:

# Test code
# Example 1
list1 = [1, 4, 5,20]
list2 = [2,10,12,50]
s = SuperIterator([iter(list1), iter(list2)])
while s.hasNext():
  print(s.next(), end=', ')
print()
# Output: 1, 2, 4, 5, 10, 12, 20, 50,

# Example 2
list1 = [12,14,16]
list2 = [4,7,9,50,100]
list3 = [6,8,10,13]
s = SuperIterator([iter(list1), iter(list2), iter(list3)])
while s.hasNext():
  print(s.next(), end=', ')
print()
# Output: 4, 6, 7, 8, 9, 10, 12, 13, 14, 16, 50, 100,

- prudent_programmer March 22, 2018 | Flag Reply


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