leetcode 341. Flatten Nested List Iterator

题目：

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].

/**
 * // 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>  {
    private Iterator<Integer> nested;
    private List<Integer> nes=new ArrayList<Integer>();
    private int index=0;
    public NestedIterator(List<NestedInteger> nestedList) {
        NesIterator(nestedList);
        nested=nes.iterator();
    }

    private void NesIterator(List<NestedInteger> nestedList) {
        for(int i=0;i<nestedList.size();i++)
        {
            if(nestedList.get(i).isInteger())
            {
                nes.add(nestedList.get(i).getInteger());
            }
            else {
                NesIterator(nestedList.get(i).getList());
            }
        }
    }
    @Override
    public Integer next() {
        index++;
        return nested.next();
    }

    @Override
    public boolean hasNext() {
           if(index<nes.size())
            return true;
        return false; 
    }
}

/**
 * Your NestedIterator object will be instantiated and called as such:
 * NestedIterator i = new NestedIterator(nestedList);
 * while (i.hasNext()) v[f()] = i.next();
 */