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			47 lines
		
	
	
		
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			47 lines
		
	
	
		
			1.8 KiB
		
	
	
	
		
			HTML
		
	
	
	
	
	
<p>如果序列 <code>X_1, X_2, ..., X_n</code> 满足下列条件,就说它是 <em>斐波那契式 </em>的:</p>
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<ul>
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	<li><code>n >= 3</code></li>
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	<li>对于所有 <code>i + 2 <= n</code>,都有 <code>X_i + X_{i+1} = X_{i+2}</code></li>
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</ul>
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<p>给定一个<strong>严格递增</strong>的正整数数组形成序列 <code>arr</code> ,找到 <code>arr</code> 中最长的斐波那契式的子序列的长度。如果一个不存在,返回  0 。</p>
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<p><em>(回想一下,子序列是从原序列  <code>arr</code> 中派生出来的,它从 <code>arr</code> 中删掉任意数量的元素(也可以不删),而不改变其余元素的顺序。例如, <code>[3, 5, 8]</code> 是 <code>[3, 4, 5, 6, 7, 8]</code> 的一个子序列)</em></p>
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<p> </p>
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<ul>
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</ul>
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<p><strong>示例 1:</strong></p>
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<pre>
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<strong>输入: </strong>arr =<strong> </strong>[1,2,3,4,5,6,7,8]
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<strong>输出: </strong>5
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<strong>解释: </strong>最长的斐波那契式子序列为 [1,2,3,5,8] 。
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</pre>
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<p><strong>示例 2:</strong></p>
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<pre>
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<strong>输入: </strong>arr =<strong> </strong>[1,3,7,11,12,14,18]
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<strong>输出: </strong>3
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<strong>解释</strong>: 最长的斐波那契式子序列有 [1,11,12]、[3,11,14] 以及 [7,11,18] 。
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</pre>
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<p> </p>
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<p><strong>提示:</strong></p>
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<ul>
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	<li><code>3 <= arr.length <= 1000</code></li>
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	<li>
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	<p><code>1 <= arr[i] < arr[i + 1] <= 10^9</code></p>
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	</li>
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</ul>
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<p> </p>
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<p><meta charset="UTF-8" />注意:本题与主站 873 题相同: <a href="https://leetcode-cn.com/problems/length-of-longest-fibonacci-subsequence/">https://leetcode-cn.com/problems/length-of-longest-fibonacci-subsequence/</a></p>
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