Package g0301_0400.s0341_flatten_nested_list_iterator

Class NestedIterator

java.lang.Object
g0301_0400.s0341_flatten_nested_list_iterator.NestedIterator
All Implemented Interfaces:
Iterator<Integer>
public class NestedIterator extends Object implements Iterator<Integer>
341 - Flatten Nested List Iterator.

Medium

You are given a nested list of integers nestedList. Each element is either an integer or a list whose elements may also be integers or other lists. Implement an iterator to flatten it.

Implement the NestedIterator class:

  • NestedIterator(List<NestedInteger> nestedList) Initializes the iterator with the nested list nestedList.
  • int next() Returns the next integer in the nested list.
  • boolean hasNext() Returns true if there are still some integers in the nested list and false otherwise.

Your code will be tested with the following pseudocode:

 initialize iterator with nestedList
 res = []
 while iterator.hasNext()
     append iterator.next() to the end of res
 return res

If res matches the expected flattened list, then your code will be judged as correct.

Example 1:

Input: nestedList = [[1,1],2,[1,1]]

Output: [1,1,2,1,1]

Explanation: By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1,1,2,1,1].

Example 2:

Input: nestedList = [1,[4,[6]]]

Output: [1,4,6]

Explanation: By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1,4,6].

Constraints:

  • 1 <= nestedList.length <= 500
  • The values of the integers in the nested list is in the range [-106, 106].