75 lines
2.0 KiB
C++
75 lines
2.0 KiB
C++
#include <vector>
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/*
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* Below is the interface for Iterator, which is already defined for you.
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* **DO NOT** modify the interface for Iterator.
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*/
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class Iterator {
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struct Data;
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Data* data;
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public:
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Iterator(const std::vector<int>& nums);
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Iterator(const Iterator& iter);
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// Returns the next element in the iteration.
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int next();
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// Returns true if the iteration has more elements.
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bool hasNext() const;
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};
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/**
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* 284. Peeking Iterator
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* Design an iterator that supports the peek operation on an existing iterator in addition to the hasNext and the next operations.
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*
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* Implement the PeekingIterator class:
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*
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* PeekingIterator(Iterator<int> nums) Initializes the object with the given integer iterator iterator.
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* int next() Returns the next element in the array and moves the pointer to the next element.
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* boolean hasNext() Returns true if there are still elements in the array.
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* int peek() Returns the next element in the array without moving the pointer.
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* Note: Each language may have a different implementation of the constructor and Iterator, but they all support the int next() and boolean hasNext() functions.
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*/
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class PeekingIterator : public Iterator {
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private:
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int x = 0;
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bool isEmpty = false;
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public:
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explicit PeekingIterator(const std::vector<int>& nums) : Iterator(nums) {
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// Initialize any member here.
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// **DO NOT** save a copy of nums and manipulate it directly.
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// You should only use the Iterator interface methods.
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if (!Iterator::hasNext())
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isEmpty = true;
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else
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this->x = Iterator::next();
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}
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// Returns the next element in the iteration without advancing the iterator.
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int peek() const {
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return x;
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}
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// hasNext() and next() should behave the same as in the Iterator interface.
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// Override them if needed.
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int next() {
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if (this->isEmpty)
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return -1;
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auto ret = this->x;
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if (Iterator::hasNext()) {
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this->x = Iterator::next();
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} else {
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this->isEmpty = true;
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}
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return ret;
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}
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bool hasNext() const {
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return !this->isEmpty;
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}
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}; |