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55 lines
2.6 KiB
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55 lines
2.6 KiB
HTML
<p>There are <code>n</code> rooms you need to visit, labeled from <code>0</code> to <code>n - 1</code>. Each day is labeled, starting from <code>0</code>. You will go in and visit one room a day.</p>
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<p>Initially on day <code>0</code>, you visit room <code>0</code>. The <strong>order</strong> you visit the rooms for the coming days is determined by the following <strong>rules</strong> and a given <strong>0-indexed</strong> array <code>nextVisit</code> of length <code>n</code>:</p>
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<ul>
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<li>Assuming that on a day, you visit room <code>i</code>,</li>
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<li>if you have been in room <code>i</code> an <strong>odd</strong> number of times (<strong>including</strong> the current visit), on the <strong>next</strong> day you will visit a room with a <strong>lower or equal room number</strong> specified by <code>nextVisit[i]</code> where <code>0 <= nextVisit[i] <= i</code>;</li>
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<li>if you have been in room <code>i</code> an <strong>even</strong> number of times (<strong>including</strong> the current visit), on the <strong>next</strong> day you will visit room <code>(i + 1) mod n</code>.</li>
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</ul>
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<p>Return <em>the label of the <strong>first</strong> day where you have been in <strong>all</strong> the rooms</em>. It can be shown that such a day exists. Since the answer may be very large, return it <strong>modulo</strong> <code>10<sup>9</sup> + 7</code>.</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> nextVisit = [0,0]
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<strong>Output:</strong> 2
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<strong>Explanation:</strong>
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- On day 0, you visit room 0. The total times you have been in room 0 is 1, which is odd.
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On the next day you will visit room nextVisit[0] = 0
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- On day 1, you visit room 0, The total times you have been in room 0 is 2, which is even.
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On the next day you will visit room (0 + 1) mod 2 = 1
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- On day 2, you visit room 1. This is the first day where you have been in all the rooms.
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</pre>
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<p><strong>Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> nextVisit = [0,0,2]
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<strong>Output:</strong> 6
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<strong>Explanation:</strong>
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Your room visiting order for each day is: [0,0,1,0,0,1,2,...].
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Day 6 is the first day where you have been in all the rooms.
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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> nextVisit = [0,1,2,0]
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<strong>Output:</strong> 6
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<strong>Explanation:</strong>
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Your room visiting order for each day is: [0,0,1,1,2,2,3,...].
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Day 6 is the first day where you have been in all the rooms.
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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>n == nextVisit.length</code></li>
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<li><code>2 <= n <= 10<sup>5</sup></code></li>
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<li><code>0 <= nextVisit[i] <= i</code></li>
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</ul>
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