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39 lines
1.3 KiB
HTML
39 lines
1.3 KiB
HTML
<p>There are <code>n</code> bulbs that are initially off. You first turn on all the bulbs, then you turn off every second bulb.</p>
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<p>On the third round, you toggle every third bulb (turning on if it's off or turning off if it's on). For the <code>i<sup>th</sup></code> round, you toggle every <code>i</code> bulb. For the <code>n<sup>th</sup></code> round, you only toggle the last bulb.</p>
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<p>Return <em>the number of bulbs that are on after <code>n</code> rounds</em>.</p>
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2020/11/05/bulb.jpg" style="width: 421px; height: 321px;" />
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<pre>
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<strong>Input:</strong> n = 3
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<strong>Output:</strong> 1
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<strong>Explanation:</strong> At first, the three bulbs are [off, off, off].
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After the first round, the three bulbs are [on, on, on].
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After the second round, the three bulbs are [on, off, on].
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After the third round, the three bulbs are [on, off, off].
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So you should return 1 because there is only one bulb is on.</pre>
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<p><strong>Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> n = 0
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<strong>Output:</strong> 0
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</pre>
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<p><strong>Example 3:</strong></p>
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<pre>
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<strong>Input:</strong> n = 1
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<strong>Output:</strong> 1
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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>0 <= n <= 10<sup>9</sup></code></li>
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</ul>
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