Package g0301_0400.s0341_flatten_nested_list_iterator

Class 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].