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40 lines
1.4 KiB
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40 lines
1.4 KiB
HTML
<p>Given an array <code>nums</code> of integers, return the <strong>length</strong> of the longest arithmetic subsequence in <code>nums</code>.</p>
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<p>Recall that a <em>subsequence</em> of an array <code>nums</code> is a list <code>nums[i<sub>1</sub>], nums[i<sub>2</sub>], ..., nums[i<sub>k</sub>]</code> with <code>0 <= i<sub>1</sub> < i<sub>2</sub> < ... < i<sub>k</sub> <= nums.length - 1</code>, and that a sequence <code>seq</code> is <em>arithmetic</em> if <code>seq[i+1] - seq[i]</code> are all the same value (for <code>0 <= i < seq.length - 1</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> nums = [3,6,9,12]
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<strong>Output:</strong> 4
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<strong>Explanation: </strong>
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The whole array is an arithmetic sequence with steps of length = 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> nums = [9,4,7,2,10]
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<strong>Output:</strong> 3
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<strong>Explanation: </strong>
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The longest arithmetic subsequence is [4,7,10].
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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> nums = [20,1,15,3,10,5,8]
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<strong>Output:</strong> 4
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<strong>Explanation: </strong>
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The longest arithmetic subsequence is [20,15,10,5].
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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>2 <= nums.length <= 1000</code></li>
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<li><code>0 <= nums[i] <= 500</code></li>
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</ul>
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