Package g0301_0400.s0341_flatten_nested_list_iterator

Class NestedIterator

java.lang.Object
g0301_0400.s0341_flatten_nested_list_iterator.NestedIterator
All Implemented Interfaces:
java.util.Iterator<java.lang.Integer>
public class NestedIterator extends java.lang.Object implements java.util.Iterator<java.lang.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].

  • Constructor Summary

    Constructors
    Constructor
    Description
    NestedIterator(java.util.List<NestedInteger> nestedList)
     

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    hasNext()
     
    java.lang.Integer
    next()
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    Methods inherited from interface java.util.Iterator

    forEachRemaining, remove

  • Constructor Details

    • NestedIterator

      public NestedIterator(java.util.List<NestedInteger> nestedList)

  • Method Details

    • next

      public java.lang.Integer next()
      Specified by:
      next in interface java.util.Iterator<java.lang.Integer>

    • hasNext

      public boolean hasNext()
      Specified by:
      hasNext in interface java.util.Iterator<java.lang.Integer>