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72 lines
3.0 KiB
HTML
72 lines
3.0 KiB
HTML
<p>Design a data structure that keeps track of the values in it and answers some queries regarding their frequencies.</p>
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<p>Implement the <code>FrequencyTracker</code> class.</p>
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<ul>
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<li><code>FrequencyTracker()</code>: Initializes the <code>FrequencyTracker</code> object with an empty array initially.</li>
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<li><code>void add(int number)</code>: Adds <code>number</code> to the data structure.</li>
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<li><code>void deleteOne(int number)</code>: Deletes <strong>one</strong> occurrence of <code>number</code> from the data structure. The data structure <strong>may not contain</strong> <code>number</code>, and in this case nothing is deleted.</li>
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<li><code>bool hasFrequency(int frequency)</code>: Returns <code>true</code> if there is a number in the data structure that occurs <code>frequency</code> number of times, otherwise, it returns <code>false</code>.</li>
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</ul>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<pre>
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<strong>Input</strong>
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["FrequencyTracker", "add", "add", "hasFrequency"]
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[[], [3], [3], [2]]
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<strong>Output</strong>
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[null, null, null, true]
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<strong>Explanation</strong>
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FrequencyTracker frequencyTracker = new FrequencyTracker();
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frequencyTracker.add(3); // The data structure now contains [3]
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frequencyTracker.add(3); // The data structure now contains [3, 3]
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frequencyTracker.hasFrequency(2); // Returns true, because 3 occurs twice
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</pre>
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<p><strong class="example">Example 2:</strong></p>
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<pre>
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<strong>Input</strong>
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["FrequencyTracker", "add", "deleteOne", "hasFrequency"]
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[[], [1], [1], [1]]
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<strong>Output</strong>
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[null, null, null, false]
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<strong>Explanation</strong>
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FrequencyTracker frequencyTracker = new FrequencyTracker();
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frequencyTracker.add(1); // The data structure now contains [1]
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frequencyTracker.deleteOne(1); // The data structure becomes empty []
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frequencyTracker.hasFrequency(1); // Returns false, because the data structure is empty
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</pre>
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<p><strong class="example">Example 3:</strong></p>
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<pre>
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<strong>Input</strong>
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["FrequencyTracker", "hasFrequency", "add", "hasFrequency"]
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[[], [2], [3], [1]]
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<strong>Output</strong>
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[null, false, null, true]
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<strong>Explanation</strong>
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FrequencyTracker frequencyTracker = new FrequencyTracker();
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frequencyTracker.hasFrequency(2); // Returns false, because the data structure is empty
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frequencyTracker.add(3); // The data structure now contains [3]
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frequencyTracker.hasFrequency(1); // Returns true, because 3 occurs once
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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 <= number <= 10<sup>5</sup></code></li>
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<li><code>1 <= frequency <= 10<sup>5</sup></code></li>
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<li>At most, <code>2 * 10<sup>5</sup></code> calls will be made to <code>add</code>, <code>deleteOne</code>, and <code>hasFrequency</code> in <strong>total</strong>.</li>
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</ul>
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