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| 1 | +// Below is the interface for Iterator, which is already defined for you. |
| 2 | +// **DO NOT** modify the interface for Iterator. |
| 3 | +class Iterator { |
| 4 | + struct Data; |
| 5 | + Data* data; |
| 6 | +public: |
| 7 | + Iterator(const vector<int>& nums); |
| 8 | + Iterator(const Iterator& iter); |
| 9 | + virtual ~Iterator(); |
| 10 | + // Returns the next element in the iteration. |
| 11 | + int next(); |
| 12 | + // Returns true if the iteration has more elements. |
| 13 | + bool hasNext() const; |
| 14 | +}; |
| 15 | + |
| 16 | + |
| 17 | +class PeekingIterator : public Iterator { |
| 18 | + bool hasPeeked; |
| 19 | + int peekElement; |
| 20 | +public: |
| 21 | + PeekingIterator(const vector<int>& nums) : Iterator(nums) { |
| 22 | + // Initialize any member here. |
| 23 | + // **DO NOT** save a copy of nums and manipulate it directly. |
| 24 | + // You should only use the Iterator interface methods. |
| 25 | + peekElement = 0; |
| 26 | + hasPeeked = false; |
| 27 | + } |
| 28 | + |
| 29 | + // Returns the next element in the iteration without advancing the iterator. |
| 30 | + int peek() { |
| 31 | + if (!hasPeeked) { |
| 32 | + peekElement = Iterator::next(); |
| 33 | + hasPeeked = true; |
| 34 | + } |
| 35 | + return peekElement; |
| 36 | + } |
| 37 | + |
| 38 | + // hasNext() and next() should behave the same as in the Iterator interface. |
| 39 | + // Override them if needed. |
| 40 | + int next() { |
| 41 | + if (hasPeeked) { |
| 42 | + hasPeeked = false; |
| 43 | + return peekElement; |
| 44 | + } |
| 45 | + return Iterator::next(); |
| 46 | + } |
| 47 | + |
| 48 | + bool hasNext() const { |
| 49 | + if (hasPeeked) return true; |
| 50 | + return Iterator::hasNext(); |
| 51 | + } |
| 52 | +}; |
| 53 | + |
| 54 | +/* |
| 55 | +class PeekingIterator : public Iterator { |
| 56 | +public: |
| 57 | + PeekingIterator(const vector<int>& nums) : Iterator(nums) { |
| 58 | + // Initialize any member here. |
| 59 | + // **DO NOT** save a copy of nums and manipulate it directly. |
| 60 | + // You should only use the Iterator interface methods. |
| 61 | + } |
| 62 | + |
| 63 | + // Returns the next element in the iteration without advancing the iterator. |
| 64 | + int peek() { |
| 65 | + Iterator(*this).next(); |
| 66 | + } |
| 67 | + |
| 68 | + // hasNext() and next() should behave the same as in the Iterator interface. |
| 69 | + // Override them if needed. |
| 70 | + int next() { |
| 71 | + return Iterator::next(); |
| 72 | + } |
| 73 | + |
| 74 | + bool hasNext() const { |
| 75 | + return Iterator::hasNext(); |
| 76 | + } |
| 77 | +}; |
| 78 | +*/ |
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