LeetCode 284. 顶端迭代器

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？

# Below is the interface for Iterator, which is already defined for you.
#
# class Iterator:
#     def __init__(self, nums):
#         """
#         Initializes an iterator object to the beginning of a list.
#         :type nums: List[int]
#         """
#
#     def hasNext(self):
#         """
#         Returns true if the iteration has more elements.
#         :rtype: bool
#         """
#
#     def next(self):
#         """
#         Returns the next element in the iteration.
#         :rtype: int
#         """
class PeekingIterator:
    def __init__(self, iterator):
        """
        Initialize your data structure here.
        :type iterator: Iterator
        """
        self.iter = iterator
        self.temp = []
    def peek(self):
        """
        Returns the next element in the iteration without advancing the iterator.
        :rtype: int
        """
        if len(self.temp)>0:
            return self.temp[-1]
        else:
            self.temp.append(self.iter.next())
            return self.temp[-1]
    def next(self):
        """
        :rtype: int
        """
        if len(self.temp)>0:
            return self.temp.pop()
        else:
            return self.iter.next()
    def hasNext(self):
        """
        :rtype: bool
        """
        if len(self.temp)>0:
            return True
        else:
            return self.iter.hasNext()
# Your PeekingIterator object will be instantiated and called as such:
# iter = PeekingIterator(Iterator(nums))
# while iter.hasNext():
#     val = iter.peek()   # Get the next element but not advance the iterator.
#     iter.next()         # Should return the same value as [val].