341. Flatten Nested List Iterator

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]

.

嵌套的容器，设计一个迭代器，以便顺序访问里面的元素。

一个个判断逻辑有些混乱，直接递归全部取出来，塞入ArrayList，返回ArrayList的迭代器就好了。

public class NestedIterator implements Iterator<Integer>
{

ArrayList<Integer> arraylist;
Iterator<Integer> it;
public NestedIterator(List<NestedInteger> nestedList)
{
arraylist=new ArrayList<>();
getval(nestedList);
it=arraylist.iterator();
}

@Override
public Integer next()
{
return it.next();
}

@Override
public boolean hasNext()
{
return it.hasNext();
}

public void getval(List<NestedInteger> nestedList)
{
for(NestedInteger nestinteger : nestedList)
if(nestinteger.isInteger())
arraylist.add(nestinteger.getInteger());
else {
getval(nestinteger.getList());
}
}

}