162. Find Peak Element

最新推荐文章于 2021-09-15 01:00:00 发布

原创最新推荐文章于 2021-09-15 01:00:00 发布 · 246 阅读

0 ·

CC 4.0 BY-SA版权

本文介绍了一种高效的算法来寻找数组中的峰值元素。峰值元素是指比其相邻元素大的元素。通过使用二分查找法，该算法能在O(log n)的时间复杂度内找到符合条件的峰值元素，并返回其索引。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

A peak element is an element that is greater than its neighbors.

Given an input array nums, where nums[i] ≠ nums[i+1], find a peak element and return its index.

The array may contain multiple peaks, in that case return the index to any one of the peaks is fine.

You may imagine that nums[-1] = nums[n] = -∞.

Example 1:

Input: nums = [1,2,3,1]
Output: 2
Explanation: 3 is a peak element and your function should return the index number 2.

Example 2:

Input: nums = [1,2,1,3,5,6,4]
Output: 1 or 5 
Explanation: Your function can return either index number 1 where the peak element is 2, 
             or index number 5 where the peak element is 6.

class Solution {
public int findPeakElement(int[] nums) {
int first = 0;
int last = nums.length-1;

while(first+1<last){
int middle = first+(last-first)/2;

if(nums[middle]> nums[middle-1] && nums[middle]>nums[middle+1]){
return middle;
}
else if(nums[middle]<nums[middle-1]){
last = middle;
}
else if(nums[middle+1]>nums[middle]){
first = middle;
}
}

if(nums[first]<nums[last]){
return last;
}
else {
return first;
}

}
}