Binary Search : PeakElement.cpp

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