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64 lines
1.6 KiB
HTML
64 lines
1.6 KiB
HTML
符合下列属性的数组 <code>arr</code> 称为 <strong>山脉数组</strong> ：
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<ul>
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<li><code>arr.length >= 3</code></li>
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<li>存在 <code>i</code>（<code>0 < i < arr.length - 1</code>）使得：
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<ul>
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<li><code>arr[0] < arr[1] < ... arr[i-1] < arr[i] </code></li>
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<li><code>arr[i] > arr[i+1] > ... > arr[arr.length - 1]</code></li>
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</ul>
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</li>
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</ul>
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<p>给你由整数组成的山脉数组 <code>arr</code> ，返回任何满足 <code>arr[0] < arr[1] < ... arr[i - 1] < arr[i] > arr[i + 1] > ... > arr[arr.length - 1]</code> 的下标 <code>i</code> 。</p>
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<p> </p>
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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 = [0,1,0]
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<strong>输出：</strong>1
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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 = [0,2,1,0]
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<strong>输出：</strong>1
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</pre>
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<p><strong>示例 3：</strong></p>
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<pre>
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<strong>输入：</strong>arr = [0,10,5,2]
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<strong>输出：</strong>1
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</pre>
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<p><strong>示例 4：</strong></p>
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<pre>
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<strong>输入：</strong>arr = [3,4,5,1]
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<strong>输出：</strong>2
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</pre>
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<p><strong>示例 5：</strong></p>
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<pre>
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<strong>输入：</strong>arr = [24,69,100,99,79,78,67,36,26,19]
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<strong>输出：</strong>2
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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 <= 10<sup>4</sup></code></li>
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<li><code>0 <= arr[i] <= 10<sup>6</sup></code></li>
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<li>题目数据保证 <code>arr</code> 是一个山脉数组</li>
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</ul>
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<p> </p>
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<p><strong>进阶：</strong>很容易想到时间复杂度 <code>O(n)</code> 的解决方案，你可以设计一个 <code>O(log(n))</code> 的解决方案吗？</p>
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