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 bynext 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 bynext should be: [1,4,6].

这个题不难，有想法就好实现，用队列来解决。

/** * // 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 null if this NestedInteger holds a single integer *     public List<NestedInteger> getList(); * } */public class NestedIterator implements Iterator<Integer> {    Deque<Integer> queue=new ArrayDeque<Integer>();public void putIntoQueue(List<NestedInteger> list){for(int i=0;i<list.size();i++){if(list.get(i).isInteger()){queue.offer(list.get(i).getInteger());}else{putIntoQueue(list.get(i).getList());}}}public NestedIterator(List<NestedInteger> nestedList) {putIntoQueue(nestedList);    }    public Integer next() {        return queue.poll();    }    public boolean hasNext() {    return queue.size()>0;    }}/** * Your NestedIterator object will be instantiated and called as such: * NestedIterator i = new NestedIterator(nestedList); * while (i.hasNext()) v[f()] = i.next(); */