# Peeking Iterator Problem

## Description

LeetCode Problem 284.

Design an iterator that supports the peek operation on an existing iterator in addition to the hasNext and the next operations.

Implement the PeekingIterator class:

• PeekingIterator(Iterator nums) Initializes the object with the given integer iterator iterator.
• int next() Returns the next element in the array and moves the pointer to the next element.
• boolean hasNext() Returns true if there are still elements in the array.
• int peek() Returns the next element in the array without moving the pointer.

Note: Each language may have a different implementation of the constructor and Iterator, but they all support the int next() and boolean hasNext() functions.

Example 1:

``````1
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Input
["PeekingIterator", "next", "peek", "next", "next", "hasNext"]
[[[1, 2, 3]], [], [], [], [], []]
Output
[null, 1, 2, 2, 3, false]
Explanation
PeekingIterator peekingIterator = new PeekingIterator([1, 2, 3]); // [1,2,3]
peekingIterator.next();    // return 1, the pointer moves to the next element [1,2,3].
peekingIterator.peek();    // return 2, the pointer does not move [1,2,3].
peekingIterator.next();    // return 2, the pointer moves to the next element [1,2,3]
peekingIterator.next();    // return 3, the pointer moves to the next element [1,2,3]
peekingIterator.hasNext(); // return False
``````

Constraints:

• 1 <= nums.length <= 1000
• 1 <= nums[i] <= 1000
• All the calls to next and peek are valid.
• At most 1000 calls will be made to next, hasNext, and peek.

## Sample C++ Code

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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);
*
* 		// 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:
PeekingIterator(const vector<int> &nums) : Iterator(nums)
{
}

int peek()
{
return Iterator(*this).next();
}

int next()
{
return Iterator::next();
}

bool hasNext() const
{
return Iterator::hasNext();
}
};
``````