/**
* // This is the interface that allows for creating nested lists.
* // You should not implement it, or speculate about its implementation
* public interface NestedInteger {
*
* // @return true if this NestedInteger holds a single integer, rather than a nested list.
* public boolean isInteger();
*
* // @return the single integer that this NestedInteger holds, if it holds a single integer
* // Return null if this NestedInteger holds a nested list
* public Integer getInteger();
*
* // @return the nested list that this NestedInteger holds, if it holds a nested list
* // Return empty list if this NestedInteger holds a single integer
* public List<NestedInteger> getList();
* }
*/publicclassNestedIteratorimplementsIterator<Integer>{Queue<NestedInteger> queue;publicNestedIterator(List<NestedInteger> nestedList){
queue =newLinkedList();dfs(nestedList);// Extract integers}@OverridepublicIntegernext(){return queue.poll().getInteger();}@OverridepublicbooleanhasNext(){return!queue.isEmpty();}privatevoiddfs(List<NestedInteger> nestedList){for(NestedInteger ni : nestedList){if(ni.isInteger()){
queue.offer(ni);}else{dfs(ni.getList());}}}}/**
* Your NestedIterator object will be instantiated and called as such:
* NestedIterator i = new NestedIterator(nestedList);
* while (i.hasNext()) v[f()] = i.next();
*/