Find Peak Element

题目地址：
https://leetcode.com/problems/find-peak-element/description/

题目：

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.

解题思路：
这道题就是用binary search就可以解决。

代码：

public int findPeakElement(int[] nums) {
    int start = 0;
    int end = nums.length - 1;
    while(start + 1 < end){
        int mid = start + (end - start) / 2;
        if(nums[mid] < nums[mid + 1]){
            start = mid;
        }
        else{
            end = mid;
        }
    }
    if(nums[start] < nums[end]){
        return end;
    }
    return start;
}

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