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// 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:
vector<int> cache;
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() {
if (cache.size() > 0) {
return cache[0];
}
else {
cache.push_back(Iterator::next());
}
return cache[0];
}
// hasNext() and next() should behave the same as in the Iterator interface.
// Override them if needed.
int next() {
int result;
if (cache.size() > 0) {
result = cache[0];
cache.pop_back();
}
else {
result = Iterator::next();
}
return result;
}
bool hasNext() const {
return cache.size() > 0 || Iterator::hasNext();
}
};