341. 扁平化嵌套列表迭代器

/**
 * // This is the interface that allows for creating nested lists.
 * // You should not implement it, or speculate about its implementation
 * class NestedInteger {
 *   public:
 *     // Return true if this NestedInteger holds a single integer, rather than a nested list.
 *     bool isInteger() const;
 *
 *     // Return the single integer that this NestedInteger holds, if it holds a single integer
 *     // The result is undefined if this NestedInteger holds a nested list
 *     int getInteger() const;
 *
 *     // Return the nested list that this NestedInteger holds, if it holds a nested list
 *     // The result is undefined if this NestedInteger holds a single integer
 *     const vector<NestedInteger> &getList() const;
 * };
 */

//看懂题意即可（其实就是列表的嵌套用深搜就行了）
class NestedIterator 
{
public:
    vector<int> v;
    int index = 0;
    
    NestedIterator(vector<NestedInteger> &nestedList) 
    {
        dfs(nestedList);
    }

    int next() 
    {
        return v[index++];
    }

    bool hasNext() 
    {
        if(index==v.size()) return false;
        else return true;
    }

    void dfs(vector<NestedInteger> &nestedList) 
    {
        for(int i=0;i<nestedList.size();i++) 
        {
            if(nestedList[i].isInteger()) v.push_back(nestedList[i].getInteger());
            else dfs(nestedList[i].getList());
        }
    }
};

/**
 * Your NestedIterator object will be instantiated and called as such:
 * NestedIterator i(nestedList);
 * while (i.hasNext()) cout << i.next();
 */