162. Find Peak Element

问题：求数组的任意峰值。两侧都从-∞开始向上递增。

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.

　　

方法：二分查找

low=0，high=end

mid=low和high的中值

如果mid<mid+1，则要求目标在mid+1～high

如果mid>mid+1，则要求目标在low～mid

 

代码参考：

class Solution {
public:
    int findPeakElement(vector<int>& nums) {
        int low=0, high=nums.size()-1;
        while(low<high){
            int mid=low+(high-low)/2;
            if(nums[mid]>nums[mid+1]){
                high=mid;
            }else{
                low=mid+1;
            }
        }
        return low;
    }
};