int findPeakElementHelper(vector<int>& nums, int l, int r) {
int mid = (l+r)/2;
if((mid==0 || nums[mid]>nums[mid-1]) && (mid==nums.size()-1 || nums[mid]>nums[mid+1])){
return mid;
}else if((mid==0 || nums[mid]>nums[mid-1]) && (mid<nums.size()-1 && nums[mid]<nums[mid+1])){
return findPeakElementHelper(nums,mid+1,r);
}else{
return findPeakElementHelper(nums,l,mid);
}
}
int findPeakElementHelper(vector<int>& nums, int start, int end)
{
if (start == end) return start;
int mid = (start + end) / 2;
if (mid > 0 && nums[mid] < nums[mid - 1]) {
return findPeakElementHelper(nums, start, mid - 1);
}
else if (mid < nums.size() - 1 && nums[mid] < nums[mid + 1]) {
return findPeakElementHelper(nums, mid + 1, end);
}
else {
return mid;
}
}
int findPeakElement(vector<int>& nums) {
return findPeakElementHelper(nums,0,nums.size());
}