284. 窥探迭代器
题目链接
来源:力扣(LeetCode)
链接:https://leetcode-cn.com/problems/peeking-iterator
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题目描述
请你设计一个迭代器,除了支持 hasNext 和 next 操作外,还支持 peek 操作。
实现 PeekingIterator 类:
PeekingIterator(int[] nums) 使用指定整数数组 nums 初始化迭代器。
int next() 返回数组中的下一个元素,并将指针移动到下个元素处。
bool hasNext() 如果数组中存在下一个元素,返回 true ;否则,返回 false 。
int peek() 返回数组中的下一个元素,但 不 移动指针。
示例:
输入:
["PeekingIterator", "next", "peek", "next", "next", "hasNext"]
[[[1, 2, 3]], [], [], [], [], []]
输出:
[null, 1, 2, 2, 3, false]
解释:
PeekingIterator peekingIterator = new PeekingIterator([1, 2, 3]); // [1,2,3]
peekingIterator.next(); // 返回 1 ,指针移动到下一个元素 [1,2,3]
peekingIterator.peek(); // 返回 2 ,指针未发生移动 [1,2,3]
peekingIterator.next(); // 返回 2 ,指针移动到下一个元素 [1,2,3]
peekingIterator.next(); // 返回 3 ,指针移动到下一个元素 [1,2,3]
peekingIterator.hasNext(); // 返回 False
提示:
- 1 <= nums.length <= 1000
- 1 <= nums[i] <= 1000
- 对 next 和 peek 的调用均有效
- next、hasNext 和 peek 最多调用 1000 次
进阶:你将如何拓展你的设计?使之变得通用化,从而适应所有的类型,而不只是整数型?
题目分析
- 根据题目描述模拟顶端迭代器
代码
/*
* 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);
*
* // 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:
bool hasNextElem;
int nextElem;
public:
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.
this->hasNextElem = Iterator::hasNext();
if (this->hasNextElem) { this->nextElem = Iterator::next(); }
return;
}
// Returns the next element in the iteration without advancing the iterator.
int peek() {
return this->nextElem;
}
// hasNext() and next() should behave the same as in the Iterator interface.
// Override them if needed.
int next() {
int res = this->nextElem;
this->hasNextElem = Iterator::hasNext();
if (this->hasNextElem) { this->nextElem = Iterator::next(); }
return res;
}
bool hasNext() const {
return this->hasNextElem;
}
};