import java.util.*;

public class NestedIterator implements Iterator<Integer> {

List<NestedInteger> nestedList;

Deque<NestedInteger> stack;

Deque<Integer> queue;

public NestedIterator(List<NestedInteger> nestedList) {

this.nestedList = nestedList;

stack = new LinkedList<>();

queue = new LinkedList<>();

}

private void flattenList(){

stack.addFirst(nestedList.get(0));

while(!stack.isEmpty()){

NestedInteger n = stack.pop();

if(n.isInteger()){

int num = n.getInteger();

queue.add(num);

}else {

if (n.getList() != null)

for(NestedInteger l : n.getList()){

stack.addFirst(l);

}

}

}

}

@Override

public Integer next() {

flattenList();

if(hasNext()){

return queue.poll();

}

return -1;

}

@Override

public boolean hasNext() {

return !queue.isEmpty();

}

public static void main(String [] args){

List<NestedInteger> list = new ArrayList<>();

//NestedInteger n1 = new

// NestedIterator i = new NestedIterator(nestedList);

}

}