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