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  • 341. Flatten Nested List Iterator

    /**
     * // 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 {
    public:
        stack<pair<vector<NestedInteger>::iterator, vector<NestedInteger>::iterator>> s;
        NestedIterator(vector<NestedInteger> &nestedList) {
            if (nestedList.size() > 0)
                s.push({nestedList.begin(), nestedList.end()});
            hasNext();
        }
    
        int next() {
            int res = s.top().first->getInteger();
            s.top().first++;
            return res;
        }
    
        bool hasNext() {
            while (!s.empty()) {
                auto p = s.top();
                vector<NestedInteger>::iterator cur = p.first;
                vector<NestedInteger>::iterator end = p.second;
                if (cur == end) {
                    s.pop();
                    if (!s.empty()) {
                        s.top().first++;
                    }
                }
                else if (cur->isInteger())
                    return true;
                else {
                    s.push({cur->getList().begin(), cur->getList().end()});
                }
            }
            return false;
        }
    };
    
    /**
     * Your NestedIterator object will be instantiated and called as such:
     * NestedIterator i(nestedList);
     * while (i.hasNext()) cout << i.next();
     */
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  • 原文地址:https://www.cnblogs.com/JTechRoad/p/9088468.html
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