[LeetCode]284. Peeking Iterator（C++，类，暴力）

题目链接：https://leetcode.com/problems/peeking-iterator/#/description

题意：实现个迭代器。

PeekingIterator是由Iterator继承来的，那么可以直接使用父类的hasNext和next。

关键是如何实现peek了，如何才能不迭代下去，但是可以看下一个值？

复制一下当前迭代器额。。。

// 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.
    }

    // Returns the next element in the iteration without advancing the iterator.
    int peek() {
        PeekingIterator it = *this;
        return it.next();
    }

    // hasNext() and next() should behave the same as in the Iterator interface.
    // Override them if needed.
    int next() {
        return Iterator::next();
    }

    bool hasNext() const {
        return Iterator::hasNext();
    }
};