LeetCode "Flatten Nested List Iterator"

Besides the common stack-based solutions, here is another recursive NestedIterator solution :)

class NestedIterator
{
    int currInx;
    const vector<NestedInteger> &rData;
    NestedIterator *sub;

    void move()
    {
        if (currInx < 0 || rData[currInx].isInteger() || !sub->hasNext())
        {
            if ((++currInx) < rData.size())
            {
                releaseSub();
                if (!rData[currInx].isInteger())
                {
                    // get next non-empty list
                    while (currInx < rData.size() &&
                            ( sub = new NestedIterator(const_cast<vector<NestedInteger>&>(rData[currInx].getList())),
                              (!rData[currInx].isInteger() && sub && !sub->hasNext())) )
                    {
                        currInx++;
                        releaseSub();
                    }
                }
            }
        }
        else
        {
            sub->move();
        }
    }
    //
    NestedIterator()
        :rData(vector<NestedInteger>()), currInx(-1), sub(nullptr)
    { }

    void releaseSub()
    {
        delete sub;    sub = nullptr;
    }

public:
    ~NestedIterator()
    {
        releaseSub();
    }

    NestedIterator(vector<NestedInteger> &nestedList)
        :rData(nestedList), currInx(-1), sub(nullptr)
    {
        move();
    }

    int next()
    {
        int val = 0;
        if (rData[currInx].isInteger())
        {
            val = rData[currInx].getInteger();
            move();
        }
        else
        {
            val = sub->next();
            if (!sub->hasNext()) move();
        }
        return val;
    }

    bool hasNext()
    {
        return currInx < rData.size() && (rData[currInx].isInteger() || sub->hasNext());
    }
};
时间： 2024-08-24 06:19:28

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