int findPeakElement(const vector<int> &num) {

int n = num.size();

int left = 0, right = n - 1;

while(left <= right) {

int mid = left + (right - left) / 2;

if((mid == 0 or num[mid] > num[mid - 1]) and (mid == n - 1 or num[mid] > num[mid + 1])) {

return mid;

} else {

if(mid > 0 and num[mid - 1] > num[mid]) {

right = mid - 1;

} else if(mid < n - 1 and num[mid + 1] > num[mid]) {

left = mid + 1;

}

}

}

return -1; // the program won't hit this line

}