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44 lines
2.3 KiB
HTML
44 lines
2.3 KiB
HTML
<p>Design an iterator that supports the <code>peek</code> operation on an existing iterator in addition to the <code>hasNext</code> and the <code>next</code> operations.</p>
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<p>Implement the <code>PeekingIterator</code> class:</p>
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<ul>
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<li><code>PeekingIterator(Iterator<int> nums)</code> Initializes the object with the given integer iterator <code>iterator</code>.</li>
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<li><code>int next()</code> Returns the next element in the array and moves the pointer to the next element.</li>
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<li><code>boolean hasNext()</code> Returns <code>true</code> if there are still elements in the array.</li>
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<li><code>int peek()</code> Returns the next element in the array <strong>without</strong> moving the pointer.</li>
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</ul>
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<p><strong>Note:</strong> Each language may have a different implementation of the constructor and <code>Iterator</code>, but they all support the <code>int next()</code> and <code>boolean hasNext()</code> functions.</p>
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<pre>
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<strong>Input</strong>
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["PeekingIterator", "next", "peek", "next", "next", "hasNext"]
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[[[1, 2, 3]], [], [], [], [], []]
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<strong>Output</strong>
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[null, 1, 2, 2, 3, false]
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<strong>Explanation</strong>
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PeekingIterator peekingIterator = new PeekingIterator([1, 2, 3]); // [<u><strong>1</strong></u>,2,3]
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peekingIterator.next(); // return 1, the pointer moves to the next element [1,<u><strong>2</strong></u>,3].
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peekingIterator.peek(); // return 2, the pointer does not move [1,<u><strong>2</strong></u>,3].
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peekingIterator.next(); // return 2, the pointer moves to the next element [1,2,<u><strong>3</strong></u>]
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peekingIterator.next(); // return 3, the pointer moves to the next element [1,2,3]
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peekingIterator.hasNext(); // return False
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li><code>1 <= nums.length <= 1000</code></li>
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<li><code>1 <= nums[i] <= 1000</code></li>
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<li>All the calls to <code>next</code> and <code>peek</code> are valid.</li>
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<li>At most <code>1000</code> calls will be made to <code>next</code>, <code>hasNext</code>, and <code>peek</code>.</li>
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</ul>
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<p> </p>
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<strong>Follow up:</strong> How would you extend your design to be generic and work with all types, not just integer? |