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33 lines
1.1 KiB
HTML
33 lines
1.1 KiB
HTML
<p>Given an array of integers <code>arr</code>, return <em><code>true</code> if and only if it is a valid mountain array</em>.</p>
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<p>Recall that arr is a mountain array if and only if:</p>
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<ul>
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<li><code>arr.length >= 3</code></li>
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<li>There exists some <code>i</code> with <code>0 < i < arr.length - 1</code> such that:
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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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<img src="https://assets.leetcode.com/uploads/2019/10/20/hint_valid_mountain_array.png" width="500" />
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<pre><strong>Input:</strong> arr = [2,1]
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<strong>Output:</strong> false
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</pre><p><strong>Example 2:</strong></p>
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<pre><strong>Input:</strong> arr = [3,5,5]
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<strong>Output:</strong> false
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</pre><p><strong>Example 3:</strong></p>
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<pre><strong>Input:</strong> arr = [0,3,2,1]
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<strong>Output:</strong> true
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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>4</sup></code></li>
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<li><code>0 <= arr[i] <= 10<sup>4</sup></code></li>
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</ul>
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