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.
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Note:Your solution should be in logarithmic complexity.
分析主要处理好边界问题，比如第一个元素和最后一个元素的判断，以及nums的大小。
class Solution { public: int findPeakElement(vector<int>& nums) { if(nums.size()<2) return 0; if(nums[0]>nums[1]) return 0; if(nums[nums.size()-1]>nums[nums.size()-2]) return nums.size()-1; for(int i=1;i<nums.size()-1;++i){ if(nums[i]>nums[i-1]&&nums[i]>nums[i+1]) return i; } } };