LeetCode 341. 扁平化嵌套列表迭代器

题目链接：

力扣https://leetcode-cn.com/problems/flatten-nested-list-iterator/

【分析】定义一个数组存储扁平化处理后的Integer值，dfs遍历这个NestedList，如果是数字就直接加入到数组中，否则dfs这个NestedInteger对象。

public class NestedIterator implements Iterator {

    public List list = new ArrayList();
    public int n;
    public int i;

    public void dfs(NestedInteger nest){
        if(nest.isInteger()){
            list.add(nest.getInteger());
        }else{
            for(NestedInteger ni: nest.getList()){
                dfs(ni);
            }
        }
    }

    public NestedIterator(List nestedList) {
        for(NestedInteger ni: nestedList){
            dfs(ni);
        }
        this.n = list.size();
        this.i = 0;
    }

    @Override
    public Integer next() {
        return list.get(i++);
    }

    @Override
    public boolean hasNext() {
        return i < n;
    }
}