LeetCode——Peeking Iterator

先自己写了个简单粗糙的，然后又看了提示中给的参考答案，模仿着写了一个

// Below is the interface for Iterator, which is already defined for you.// **DO NOT** modify the interface for Iterator.class Iterator {    struct Data;Data* data;public:Iterator(const vector<int>& nums);Iterator(const Iterator& iter);virtual ~Iterator();// Returns the next element in the iteration.int next();// Returns true if the iteration has more elements.bool hasNext() const;};class PeekingIterator : public Iterator {public:PeekingIterator(const vector<int>& nums):Iterator(nums) {    // Initialize any member here.    // **DO NOT** save a copy of nums and manipulate it directly.    // You should only use the Iterator interface methods.    peekedElement = Iterator::next();    hasPeeked = true;}    // Returns the next element in the iteration without advancing the iterator.int peek() {        if(!hasPeeked)    {        peekedElement = Iterator::next();        hasPeeked = true;    }                return peekedElement;}// hasNext() and next() should behave the same as in the Iterator interface.// Override them if needed.int next() {      if(hasPeeked)   {       hasPeeked = false;       return peekedElement;   }   else   {       return Iterator::next();   }}bool hasNext() const {        return hasPeeked || Iterator::hasNext();}private:    int peekedElement;    bool hasPeeked;};

基本思路是，用变量hasPeeked判断peekedElement保存的是否为所需的元素，若是，则无需调用基类的next()函数，直接使用这个变量。如此一来，增加peek功能不影响时间复杂度。