341.flatten-nested-list-iterator.cpp

/*
 * @lc app=leetcode id=341 lang=cpp
 *
 * [341] Flatten Nested List Iterator
 */

// @lc code=start
/**
 * // 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 {
  private:
    queue<int> q;

  public:
    void iter(vector<NestedInteger> &nestedList) {
        for (auto x : nestedList) {
            if (x.isInteger()) q.push(x.getInteger());
            else iter(x.getList());
        }
    }

    NestedIterator(vector<NestedInteger> &nestedList) {
        iter(nestedList);
    }

    int next() {
        int result = q.front();
        q.pop();
        return result;
    }

    bool hasNext() {
        return q.size();
    }
};

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