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41 lines
2.1 KiB
HTML
41 lines
2.1 KiB
HTML
<p>You have a set which contains all positive integers <code>[1, 2, 3, 4, 5, ...]</code>.</p>
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<p>Implement the <code>SmallestInfiniteSet</code> class:</p>
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<ul>
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<li><code>SmallestInfiniteSet()</code> Initializes the <strong>SmallestInfiniteSet</strong> object to contain <strong>all</strong> positive integers.</li>
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<li><code>int popSmallest()</code> <strong>Removes</strong> and returns the smallest integer contained in the infinite set.</li>
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<li><code>void addBack(int num)</code> <strong>Adds</strong> a positive integer <code>num</code> back into the infinite set, if it is <strong>not</strong> already in the infinite set.</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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["SmallestInfiniteSet", "addBack", "popSmallest", "popSmallest", "popSmallest", "addBack", "popSmallest", "popSmallest", "popSmallest"]
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[[], [2], [], [], [], [1], [], [], []]
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<strong>Output</strong>
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[null, null, 1, 2, 3, null, 1, 4, 5]
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<strong>Explanation</strong>
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SmallestInfiniteSet smallestInfiniteSet = new SmallestInfiniteSet();
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smallestInfiniteSet.addBack(2); // 2 is already in the set, so no change is made.
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smallestInfiniteSet.popSmallest(); // return 1, since 1 is the smallest number, and remove it from the set.
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smallestInfiniteSet.popSmallest(); // return 2, and remove it from the set.
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smallestInfiniteSet.popSmallest(); // return 3, and remove it from the set.
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smallestInfiniteSet.addBack(1); // 1 is added back to the set.
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smallestInfiniteSet.popSmallest(); // return 1, since 1 was added back to the set and
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// is the smallest number, and remove it from the set.
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smallestInfiniteSet.popSmallest(); // return 4, and remove it from the set.
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smallestInfiniteSet.popSmallest(); // return 5, and remove it from the set.
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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 <= num <= 1000</code></li>
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<li>At most <code>1000</code> calls will be made <strong>in total</strong> to <code>popSmallest</code> and <code>addBack</code>.</li>
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</ul>
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