Class PeekingIterator
- java.lang.Object
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- g0201_0300.s0284_peeking_iterator.PeekingIterator
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public class PeekingIterator extends Object implements Iterator<Integer>
284 - Peeking Iterator.Medium
Design an iterator that supports the
peek
operation on an existing iterator in addition to thehasNext
and thenext
operations.Implement the
PeekingIterator
class:PeekingIterator(Iterator<int> nums)
Initializes the object with the given integer iteratoriterator
.int next()
Returns the next element in the array and moves the pointer to the next element.boolean hasNext()
Returnstrue
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 theint next()
andboolean hasNext()
functions.Example 1:
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
andpeek
are valid. - At most
1000
calls will be made tonext
,hasNext
, andpeek
.
Follow up: How would you extend your design to be generic and work with all types, not just integer?
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Constructor Summary
Constructors Constructor Description PeekingIterator(Iterator<Integer> iterator)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
hasNext()
Integer
next()
Integer
peek()
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Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
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Methods inherited from interface java.util.Iterator
forEachRemaining, remove
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