284. 顶端迭代器

/*
 * 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;
 *        Iterator(const vector<int>& nums);
 *         Iterator(const Iterator& iter);
 *
 *         // 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() 
    {
        auto temp = *this;
        return temp.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();
    }
};