Fork me on GitHub

Flatten Nested List Iterator

Posted on

Description

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

Solution

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
/**
 * // 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:
    NestedIterator(vector<NestedInteger>& nestedList) {
        this->index = 0;
        this->list = new vector<int>();
        this->parse(nestedList);
        this->length = this->list->size();
    }
    
    void parse(vector<NestedInteger>& nestedList) {
        for(int i = 0; i < nestedList.size(); i++){
            if(nestedList[i].isInteger() == true) this->list->push_back(nestedList[i].getInteger());
            else this->parse(nestedList[i].getList());
        }
    }

    int next() {
        int ret = (*this->list)[index];
        this->index += 1;
        return ret;
    }

    bool hasNext() {
        return this->index < this->length;
    }
private:
    vector<int>* list;
    int index;
    int length;
};

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