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44 lines
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Markdown
Executable File
44 lines
1.7 KiB
Markdown
Executable File
# [162. Find Peak Element](https://leetcode.com/problems/find-peak-element/)
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## 题目
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A peak element is an element that is greater than its neighbors.
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Given an input array `nums`, where `nums[i] ≠ nums[i+1]`, find a peak element and return its index.
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The array may contain multiple peaks, in that case return the index to any one of the peaks is fine.
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You may imagine that `nums[-1] = nums[n] = -∞`.
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**Example 1:**
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Input: nums = [1,2,3,1]
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Output: 2
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Explanation: 3 is a peak element and your function should return the index number 2.
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**Example 2:**
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Input: nums = [1,2,1,3,5,6,4]
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Output: 1 or 5
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Explanation: Your function can return either index number 1 where the peak element is 2,
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or index number 5 where the peak element is 6.
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**Note:**
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Your solution should be in logarithmic complexity.
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## 题目大意
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峰值元素是指其值大于左右相邻值的元素。给定一个输入数组 nums，其中 nums[i] ≠ nums[i+1]，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，返回任何一个峰值所在位置即可。你可以假设 nums[-1] = nums[n] = -∞。
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说明:
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- 你的解法应该是 O(logN) 时间复杂度的。
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## 解题思路
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- 给出一个数组，数组里面存在多个“山峰”，(山峰的定义是，下标 `i` 比 `i-1`、`i+1` 位置上的元素都要大)，找到这个“山峰”，并输出其中一个山峰的下标。
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- 这一题是第 852 题的伪加强版，第 852 题中只存在一个山峰，这一题存在多个山峰。但是实际上搜索的代码是一样的，因为此题只要求随便输出一个山峰的下标即可。思路同第 852 题。
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