leetcode 341. Flatten Nested List Iterator

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
 * 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;
 * };
 */
class NestedIterator {
	vector<int>flat;
	int kk;
	void flatten(NestedInteger ni)
	{
		if (ni.isInteger())
		{
			flat.push_back(ni.getInteger());
			return;
		}
		const vector<NestedInteger>vv=ni.getList();
		int k = 0;
		while (k < vv.size())
		{
			flatten(vv[k]);
			k++;
		}
	}
public:
	NestedIterator(vector<NestedInteger> &nestedList) {
		for (int i = 0; i < nestedList.size();i++)
		flatten(nestedList[i]);
		kk = 0;
	}

	int next() {
		return flat[kk++];
	}

	bool hasNext() {
		return kk < flat.size();
	}
};

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

accept