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小墨
2023-12-09 18:42:21 +08:00
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leetcode/problem/peak-index-in-a-mountain-array.html
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@@ -1,33 +1,35 @@
<p>Let&#39;s call an array <code>arr</code> a <strong>mountain</strong>&nbsp;if the following properties hold:</p>
<p>An array <code>arr</code> is a <strong>mountain</strong> if the following properties hold:</p>
<ul>
<li><code>arr.length &gt;= 3</code></li>
<li>There exists some <code>i</code> with&nbsp;<code>0 &lt; i&nbsp;&lt; arr.length - 1</code>&nbsp;such that:
<li>There exists some <code>i</code> with <code>0 &lt; i &lt; arr.length - 1</code> such that:
<ul>
<li><code>arr[0] &lt; arr[1] &lt; ... arr[i-1] &lt; arr[i] </code></li>
<li><code>arr[i] &gt; arr[i+1] &gt; ... &gt; arr[arr.length - 1]</code></li>
<li><code>arr[0] &lt; arr[1] &lt; ... &lt; arr[i - 1] &lt; arr[i] </code></li>
<li><code>arr[i] &gt; arr[i + 1] &gt; ... &gt; arr[arr.length - 1]</code></li>
</ul>
</li>
</ul>
<p>Given an integer array <code>arr</code> that is <strong>guaranteed</strong> to be&nbsp;a mountain, return any&nbsp;<code>i</code>&nbsp;such that&nbsp;<code>arr[0] &lt; arr[1] &lt; ... arr[i - 1] &lt; arr[i] &gt; arr[i + 1] &gt; ... &gt; arr[arr.length - 1]</code>.</p>
<p>Given a mountain array <code>arr</code>, return the index <code>i</code> such that <code>arr[0] &lt; arr[1] &lt; ... &lt; arr[i - 1] &lt; arr[i] &gt; arr[i + 1] &gt; ... &gt; arr[arr.length - 1]</code>.</p>
<p>You must solve it in <code>O(log(arr.length))</code> time complexity.</p>
<p>&nbsp;</p>
<p><strong>Example 1:</strong></p>
<p><strong class="example">Example 1:</strong></p>
<pre>
<strong>Input:</strong> arr = [0,1,0]
<strong>Output:</strong> 1
</pre>
<p><strong>Example 2:</strong></p>
<p><strong class="example">Example 2:</strong></p>
<pre>
<strong>Input:</strong> arr = [0,2,1,0]
<strong>Output:</strong> 1
</pre>
<p><strong>Example 3:</strong></p>
<p><strong class="example">Example 3:</strong></p>
<pre>
<strong>Input:</strong> arr = [0,10,5,2]
@@ -38,10 +40,7 @@
<p><strong>Constraints:</strong></p>
<ul>
<li><code>3 &lt;= arr.length &lt;= 10<sup>4</sup></code></li>
<li><code>3 &lt;= arr.length &lt;= 10<sup>5</sup></code></li>
<li><code>0 &lt;= arr[i] &lt;= 10<sup>6</sup></code></li>
<li><code>arr</code> is <strong>guaranteed</strong> to be a mountain array.</li>
</ul>
<p>&nbsp;</p>
<strong>Follow up:</strong> Finding the <code>O(n)</code> is straightforward, could you find an <code>O(log(n))</code> solution?