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36 lines
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36 lines
1.3 KiB
HTML
<p>Given an integer array <code>arr</code> and an integer <code>difference</code>, return the length of the longest subsequence in <code>arr</code> which is an arithmetic sequence such that the difference between adjacent elements in the subsequence equals <code>difference</code>.</p>
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<p>A <strong>subsequence</strong> is a sequence that can be derived from <code>arr</code> by deleting some or no elements without changing the order of the remaining elements.</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> arr = [1,2,3,4], difference = 1
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<strong>Output:</strong> 4
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<strong>Explanation: </strong>The longest arithmetic subsequence is [1,2,3,4].</pre>
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<p><strong>Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> arr = [1,3,5,7], difference = 1
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<strong>Output:</strong> 1
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<strong>Explanation: </strong>The longest arithmetic subsequence is any single element.
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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> arr = [1,5,7,8,5,3,4,2,1], difference = -2
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<strong>Output:</strong> 4
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<strong>Explanation: </strong>The longest arithmetic subsequence is [7,5,3,1].
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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>1 <= arr.length <= 10<sup>5</sup></code></li>
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<li><code>-10<sup>4</sup> <= arr[i], difference <= 10<sup>4</sup></code></li>
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</ul>
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