struct Data;

Data* data;

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;

PeekingIterator(const vector<int>& nums) : Iterator(nums), hasPeeked(false) {

}

// 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) {

return Iterator::next();

}

int result = peekedElement;

hasPeeked = false;

return result;

}

bool hasNext() const {

return hasPeeked or Iterator::hasNext();

}

bool hasPeeked;

int peekedElement;