Package g0201_0300.s0284_peeking_iterator

Class PeekingIterator

  • All Implemented Interfaces:
    kotlin.collections.Iterator 
    
public final class PeekingIterator
 implements Iterator<Int>

    284 - Peeking Iterator.

    Medium

    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&lt;int&gt; 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:

    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 &lt;= nums.length &lt;= 1000

    • 1 &lt;= nums[i] &lt;= 1000

    • All the calls to next and peek are valid.

    • At most 1000 calls will be made to next, hasNext, and peek.

    Follow up: How would you extend your design to be generic and work with all types, not just integer?

    • Nested Class Summary

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    • Enum Constant Summary

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