341. Flatten Nested List Iterator

Posted 2020-09-27 Premiumlab

https://leetcode.com/problems/flatten-nested-list-iterator/#/description

 

Given a nested list of integers, implement an iterator to flatten it.

Each element is either an integer, or a list -- whose elements may also be integers or other lists.

Example 1:
Given the list [[1,1],2,[1,1]],

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

 

Example 2:
Given the list [1,[4,[6]]],

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

 

 

 

 

 

Sol:

 

???

 

# """
# This is the interface that allows for creating nested lists.
# You should not implement it, or speculate about its implementation
# """
#class NestedInteger(object):
#    def isInteger(self):
#        """
#        @return True if this NestedInteger holds a single integer, rather than a nested list.
#        :rtype bool
#        """
#
#    def getInteger(self):
#        """
#        @return the single integer that this NestedInteger holds, if it holds a single integer
#        Return None if this NestedInteger holds a nested list
#        :rtype int
#        """
#
#    def getList(self):
#        """
#        @return the nested list that this NestedInteger holds, if it holds a nested list
#        Return None if this NestedInteger holds a single integer
#        :rtype List[NestedInteger]
#        """

class NestedIterator(object):

    def __init__(self, nestedList):
        """
        Initialize your data structure here.
        :type nestedList: List[NestedInteger]
        """
        self.queue = collections.deque([])
        for elem in nestedList:
            if elem.isInteger():
                self.queue.append(elem.getInteger())
            else:
                newList = NestedIterator(elem.getList())
                while newList.hasNext():
                    self.queue.append(newList.next())
                    
    def hasNext(self):
        """
        :rtype: int
        """
        if self.queue:
            return True
        return False
        
    
    def next(self):
        """
        :rtype: bool
        """
        return self.queue.popleft()
        

# Your NestedIterator object will be instantiated and called as such:
# i, v = NestedIterator(nestedList), []
# while i.hasNext(): v.append(i.next())