leetcode341-扁平化嵌套列表迭代器

扁平化嵌套列表迭代器

• 递归

对于传入的List<NestedInteger> nestedList,使用迭代器获取NestedInteger,如果当前的数字是Integer,那么直接加入List中；否则，就将取出的链表传入函数中进行递归调用

/**
 * // 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();
 * }
 */
public class NestedIterator implements Iterator<Integer> {
    List<Integer> list = new ArrayList<>();
    Iterator<Integer> it = null;
    public NestedIterator(List<NestedInteger> nestedList) {
        parseNestedIterator(nestedList);
        it = list.iterator();
    }
    public void parseNestedIterator(List<NestedInteger> nestedList){
        Iterator<NestedInteger> it = nestedList.iterator();
        while(it.hasNext()){
            NestedInteger nest = it.next();
            if(nest.isInteger())    list.add(nest.getInteger());
            else{
                parseNestedIterator(nest.getList());
            }
        }
    }

    @Override
    public Integer next() {
        return it.next();
    }

    @Override
    public boolean hasNext() {
        return it.hasNext();
    }
}

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