Peeking Iterator

c++

// 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 {
private:
int m_next;
bool m_hasnext;
public:
PeekingIterator(const vector<int>& nums) : Iterator(nums) {
m_hasnext = Iterator::hasNext();
if (m_hasnext) m_next = Iterator::next();
}

int peek() {
return m_next;
}

int next() {
int t = m_next;
m_hasnext = Iterator::hasNext();
if (m_hasnext) m_next = Iterator::next();
return t;
}

bool hasNext() const {
return m_hasnext;
}
};