[LeetCode] 341. Flatten Nested List Iterator

[LeetCode] 341. Flatten Nested List Iterator

• https://leetcode.com/problems/flatten-nested-list-iterator/

풀이

• 처음 보는 유형의 문제라 조금 당황스러웠지만, 문제를 여러번 읽어보니 풀 수 있었다

/**
 * // 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:
    int flattenedListIndex = 0;
    vector<int> flattenedList = vector<int>();

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

    NestedIterator(vector<NestedInteger> &nestedList) {
        flattenList(nestedList);
    }
    
    int next() {
        return flattenedList[flattenedListIndex++];
    }
    
    bool hasNext() {
        if(flattenedListIndex < flattenedList.size()) return true;
        return false;
    }
};

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