162 Find Peak Element

来源：Leetcode

原帖：https://leetcode.com/problems/find-peak-element/

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] = -∞.

代码：

 class Solution {  
 public:  
   int findPeakElement(const vector<int> &num) {  
     int len = num.size();  
       if (len == 1) return 0;  
       int left = 0, right = len - 1;  
       int mid;  
       while (left + 1 < right) {  
         mid = left + (right - left) / 2;  
         if (num[mid] > num[mid-1] && num[mid] > num[mid+1]) return mid;  
         if (num[mid] < num[mid-1]) right = mid; // like hill climbing   
         else left = mid;  
       }  
       return num[left] > num[right] ? left : right;  
   }  
 };