Project Notes

Find Peak Element

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Description

tab: English
 
<p>A peak element is an element that is strictly greater than its neighbors.</p>
 
<p>Given a <strong>0-indexed</strong> integer array <code>nums</code>, find a peak element, and return its index. If the array contains multiple peaks, return the index to <strong>any of the peaks</strong>.</p>
 
<p>You may imagine that <code>nums[-1] = nums[n] = -&infin;</code>. In other words, an element is always considered to be strictly greater than a neighbor that is outside the array.</p>
 
<p>You must write an algorithm that runs in <code>O(log n)</code> time.</p>
 
<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
 
<pre>
<strong>Input:</strong> nums = [1,2,3,1]
<strong>Output:</strong> 2
<strong>Explanation:</strong> 3 is a peak element and your function should return the index number 2.</pre>
 
<p><strong class="example">Example 2:</strong></p>
 
<pre>
<strong>Input:</strong> nums = [1,2,1,3,5,6,4]
<strong>Output:</strong> 5
<strong>Explanation:</strong> Your function can return either index number 1 where the peak element is 2, or index number 5 where the peak element is 6.</pre>
 
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>
 
<ul>
	<li><code>1 &lt;= nums.length &lt;= 1000</code></li>
	<li><code>-2<sup>31</sup> &lt;= nums[i] &lt;= 2<sup>31</sup> - 1</code></li>
	<li><code>nums[i] != nums[i + 1]</code> for all valid <code>i</code>.</li>
</ul>
 
 
 
---
 
[submissions](https://leetcode.com/problems/find-peak-element/submissions/) | [solutions](https://leetcode.com/problems/find-peak-element/solutions/)
 
 
tab: 中文
 
<p>峰值元素是指其值严格大于左右相邻值的元素。</p>
 
<p>给你一个整数数组&nbsp;<code>nums</code>，找到峰值元素并返回其索引。数组可能包含多个峰值，在这种情况下，返回 <strong>任何一个峰值</strong> 所在位置即可。</p>
 
<p>你可以假设&nbsp;<code>nums[-1] = nums[n] = -∞</code> 。</p>
 
<p>你必须实现时间复杂度为 <code>O(log n)</code><em> </em>的算法来解决此问题。</p>
 
<p>&nbsp;</p>
 
<p><strong>示例 1：</strong></p>
 
<pre>
<strong>输入：</strong>nums = <code>[1,2,3,1]</code>
<strong>输出：</strong>2
<strong>解释：</strong>3 是峰值元素，你的函数应该返回其索引 2。</pre>
 
<p><strong>示例&nbsp;2：</strong></p>
 
<pre>
<strong>输入：</strong>nums = <code>[</code>1,2,1,3,5,6,4]
<strong>输出：</strong>1 或 5 
<strong>解释：</strong>你的函数可以返回索引 1，其峰值元素为 2；
&nbsp;    或者返回索引 5， 其峰值元素为 6。
</pre>
 
<p>&nbsp;</p>
 
<p><strong>提示：</strong></p>
 
<ul>
	<li><code>1 &lt;= nums.length &lt;= 1000</code></li>
	<li><code>-2<sup>31</sup> &lt;= nums[i] &lt;= 2<sup>31</sup> - 1</code></li>
	<li>对于所有有效的 <code>i</code> 都有 <code>nums[i] != nums[i + 1]</code></li>
</ul>
 
 
 
---
 
[提交记录](https://leetcode.cn/problems/find-peak-element/submissions/) | [题解](https://leetcode.cn/problems/find-peak-element/solution/)

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