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50 lines
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50 lines
1.7 KiB
HTML
<p>Your car starts at position <code>0</code> and speed <code>+1</code> on an infinite number line. Your car can go into negative positions. Your car drives automatically according to a sequence of instructions <code>'A'</code> (accelerate) and <code>'R'</code> (reverse):</p>
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<ul>
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<li>When you get an instruction <code>'A'</code>, your car does the following:
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<ul>
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<li><code>position += speed</code></li>
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<li><code>speed *= 2</code></li>
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</ul>
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</li>
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<li>When you get an instruction <code>'R'</code>, your car does the following:
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<ul>
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<li>If your speed is positive then <code>speed = -1</code></li>
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<li>otherwise <code>speed = 1</code></li>
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</ul>
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Your position stays the same.</li>
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</ul>
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<p>For example, after commands <code>"AAR"</code>, your car goes to positions <code>0 --> 1 --> 3 --> 3</code>, and your speed goes to <code>1 --> 2 --> 4 --> -1</code>.</p>
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<p>Given a target position <code>target</code>, return <em>the length of the shortest sequence of instructions to get there</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> target = 3
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<strong>Output:</strong> 2
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<strong>Explanation:</strong>
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The shortest instruction sequence is "AA".
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Your position goes from 0 --> 1 --> 3.
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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> target = 6
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<strong>Output:</strong> 5
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<strong>Explanation:</strong>
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The shortest instruction sequence is "AAARA".
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Your position goes from 0 --> 1 --> 3 --> 7 --> 7 --> 6.
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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 <= target <= 10<sup>4</sup></code></li>
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</ul>
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