LeetCode 162. Find Peak Element

最新推荐文章于 2025-05-20 17:29:58 发布

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最新推荐文章于 2025-05-20 17:29:58 发布

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分类专栏： LeetCode 题解 Multiple Passes

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本文介绍了一个C++函数，用于在一个整数数组中查找峰值元素并返回其索引。峰值元素定义为大于其相邻元素的元素。文章提供的代码实现了一种有效的算法来定位峰值，即使数组包含多个峰值也能成功找到其中之一。

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#include <iostream>
#include <vector>
using namespace std;

/*
  A peak element is an element that is greater than its neighbors.
  Given an input array where nums[i] != nums[i+1], find a peak element
  and return its index.
  The array may contains muitiple peaks, in that case return the index to
  any one of the peaks is fine.
  For example:
  Given [1, 2, 3, 1], 3 is a peak element and your function should return
  the index number 2.
*/

int findPeakElement(vector<int>& nums) {
  if(nums.size() == 0) return -1;
  int n = nums.size();
  if(n == 1) return 0;
  int left = 0, right = n - 1;
  int mid = 0;
  while(left < right) {
    int mid = (left + right) / 2;
    if((mid == 0 || nums[mid] > nums[mid - 1]) && (mid == n - 1 || nums[mid] >= nums[mid + 1])) return mid;
    else if(mid > 0 && nums[mid - 1] > nums[mid]) right = mid - 1;
    else left = mid + 1;
  }
  return mid;
}

int main(void) {
  vector<int> nums{4, 2, 1, 1};
  cout << findPeakElement(nums) << endl;
}