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51 lines
2.5 KiB
HTML
51 lines
2.5 KiB
HTML
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<p>There is a safe protected by a password. The password is a sequence of <code>n</code> digits where each digit can be in the range <code>[0, k - 1]</code>.</p>
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<p>The safe has a peculiar way of checking the password. When you enter in a sequence, it checks the <strong>most recent </strong><code>n</code><strong> digits</strong> that were entered each time you type a digit.</p>
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<ul>
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<li>For example, the correct password is <code>"345"</code> and you enter in <code>"012345"</code>:
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<ul>
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<li>After typing <code>0</code>, the most recent <code>3</code> digits is <code>"0"</code>, which is incorrect.</li>
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<li>After typing <code>1</code>, the most recent <code>3</code> digits is <code>"01"</code>, which is incorrect.</li>
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<li>After typing <code>2</code>, the most recent <code>3</code> digits is <code>"012"</code>, which is incorrect.</li>
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<li>After typing <code>3</code>, the most recent <code>3</code> digits is <code>"123"</code>, which is incorrect.</li>
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<li>After typing <code>4</code>, the most recent <code>3</code> digits is <code>"234"</code>, which is incorrect.</li>
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<li>After typing <code>5</code>, the most recent <code>3</code> digits is <code>"345"</code>, which is correct and the safe unlocks.</li>
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</ul>
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</li>
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</ul>
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<p>Return <em>any string of <strong>minimum length</strong> that will unlock the safe <strong>at some point</strong> of entering it</em>.</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> n = 1, k = 2
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<strong>Output:</strong> "10"
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<strong>Explanation:</strong> The password is a single digit, so enter each digit. "01" would also unlock the safe.
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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> n = 2, k = 2
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<strong>Output:</strong> "01100"
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<strong>Explanation:</strong> For each possible password:
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- "00" is typed in starting from the 4<sup>th</sup> digit.
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- "01" is typed in starting from the 1<sup>st</sup> digit.
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- "10" is typed in starting from the 3<sup>rd</sup> digit.
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- "11" is typed in starting from the 2<sup>nd</sup> digit.
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Thus "01100" will unlock the safe. "01100", "10011", and "11001" would also unlock the safe.
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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 <= n <= 4</code></li>
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<li><code>1 <= k <= 10</code></li>
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<li><code>1 <= k<sup>n</sup> <= 4096</code></li>
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</ul>
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