162. Find Peak Element 再做一遍！

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本文介绍了一种在给定数组中寻找峰值元素的算法，并确保解决方案的时间复杂度为对数级别。峰值元素是指比其邻居大的元素。

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

Given an input array where num[i] ≠ num[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 num[-1] = num[n] = -∞.

For example, in array [1, 2, 3, 1], 3 is a peak element and your function should return the index number 2.

Note:

Your solution should be in logarithmic complexity.

public class Solution {
    public int findPeakElement(int[] nums) {
       return findMax(nums,0,nums.length-1);
    }
    
    public int findMax(int[] nums,int left,int right){
        if(left==right) return left;
        else if(left+1==right){
            if(nums[left]>nums[right]) return left;
            else return right;
        }else{
            int mid = (left+right)/2;
            if(nums[mid]>nums[mid+1]&&nums[mid]>nums[mid-1]) return mid;
            else if(nums[mid]<nums[mid+1]&&nums[mid]>nums[mid-1]) return findMax(nums,mid+1,right);
            else return findMax(nums,left,mid-1);
        }
    }
}