LeetCode:Find Peak Element

Find Peak Element
Total Accepted: 52148 
Total Submissions: 159699 
Difficulty: Medium
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.
Credits: Special thanks to @ts for adding this problem and creating all test cases.
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Array Binary Search
code:

class Solution {
public:
    int findPeakElement(vector<int>& nums) {
        int lo = 0, hi = nums.size() - 1;
        while(lo < hi) {
            int mid1 = (lo + hi)>>1;
            int mid2 = mid1 + 1;
            if(nums[mid1] < nums[mid2]) lo = mid2;
            else hi = mid1;
        }
        return lo;
    }
};